G,
You don't say how old your children are. That would make a huge difference in my decision.
Three weeks IS a long time. But I used to go for nearly that long to stay with my cousins and their two adoring, elderly aunts, in a small town on a lake. These were some of the happiest times of my entire childhood. At that point, I could BE a pure child, not a daughter. There were no expectations or roles except for us to be polite and follow the rules and have a good time together. I am still extremely close to my cousin today, and I bless my mother for allowing me to have these experiences away from my nuclear family and to develop and deepen my love for my cousin; our relationship has been so important to us both in our adult lives. I was about eight when I started leaving on these summer trips away, and when I was twelve, I went to California where my cousin actually lived and spent a month. It's incredible now to look back on that month and realize I got to know a state, and a city---San Francisco/Berkeley---that otherwise I never would have known so closely and so well.
Those experiences were particularly important to my cousin, a shy, withdrawn little girl who had a lot of trouble making friends. She and I were born one month apart; we have middle names for each other's mother, as our mothers were very close as sisters. Even at a young age, I knew I was supporting her and that we had a special bond I did not share with my sisters. When her family moved to California, it really got rough and that's when I came to be with her that summer. My aunt felt my cousin was really only close to me growing up. She is still shy and quiet. I love her dearly. It was a bonding experience to share the same bed with her in that pretty little white house, to go to county fairs and movies---one week we saw the same movie three times!---to walk to the fields and feed the horses, just to BE. When my mother died, it was not to my sisters that I went, but to my cousin. She was and is there for me. If we had not been allowed to spend time together at the little white house near the lake, I don't think we would be this close or supportive of each other today. So think what long-term benefits your kids could get by bonding in a special way with their grandparents (and perhaps others?) It's not just about taking a trip; it's about creating lasting memories and closeness with loved ones. I hope your children can have such experiences.
One thing---I know I am digressing, but this is somewhat of a point---my cousin desperately wanted friends in California. It was very difficult. There were actually "sororities" in the junior high and high school she attended, large snobbish cliques. To take a girl from the midwest who is shy to begin with and stick her in this environment was a recipe for disaster. Before I came for that month in Berkeley, she decided that she would give a luncheon party when I was there. She thought the popular kids would like me, and she could thus be liked herself, so she invited the popular girls (oh, the pain, when I think of it now; it was so sad.) When I arrived, the party was already being planned, but we spent one entire day fixing the table together, making the cake, the sandwiches, setting out little nut cups. The day of the party arrived. Every one of the eight girls she invited said they would come. They were supposed to be there at noon. 12:15. 12:30. The clock began to move ever more slowly. 1 PM. I sat at the table, miserably staring at the beautiful settings, feeling the minute hand of the clock go around and around. At 2 PM we quietly and silently removed all the items from the table. At 4, my aunt came home. I will never forget her leaning against the sideboard, saying, "You wish so much these things would happen to you, not your children," a stricken look on her face. She was white.
To this day my cousin and I have never spoken of that awful day. All the girls accepted, and then deliberately stayed away, just to hurt her. But I was there for her. And I learned greatly from the experience, because my mother allowed me to have it.
Your in-laws keep asking because they very much want to do this, I expect, and hope someday you'll say yes. I hope you'll evaluate what positive experiences they could have, and that even in a negative situation they would learn a great deal.
Growing up, also, I spent one weekend per month with my paternal grandmother. The rules were all different and my mother would have been unhappy about the laxity. There was plenty of candy at all times, and movies my mother (and father) would not have wanted me to see. But thank God I did; it would be hard to imagine missing "An Affair to Remember," weeping in the balcony. That grandmother became the greatest support of my life outside of my father; the person who loved me completely and unconditionally. My mother was a control freak and a stickler, but I am so glad she let down and allowed me to have these relationships and experiences. She didn't always approve of my grandmother, or even particularly like her, but she let us be together. What a priceless gift to give your child; it's true love. OK, my grandmother should not have spoiled me so much. But I bless her for it. The rules at home were rigid and inflexible and any movies of any adult nature were forbidden. With Grandma, I learned to grow up a little, and certainly how to relax.
I was equally close to my maternal grandmother. That's because my mother liked to travel and NOT take her kids, so we would go there and stay. I loved that environment as well and was extremely close also to that grandmother, plus all the aunts, uncles, and cousins always flooding the house. Thank you, Mom, for all you did in this regard to give me such a happy childhood, with some time away from you to act and react differently.
Also, as a parent of adult children, two of whom we are very close to, I have to say that I think it's wise parenting to let go. How will your kids learn to fly if you are always there to hold up their wings? How will they learn to follow guidelines and rules you have set down, when they are on their own, if they never are free of your aura of control? They have to learn to make choices and decisions and they WILL make mistakes. And that is how they truly will learn.
If I were you, I would consider how your children may feel about you someday if you deny them the opportunity to take trips and travel with their grandparents, that is, assuming your children wish to go, another thing you haven't said. They may resent you and rebel. (They'll rebel anyway, but I'm not in favor of giving them excuses.) You don't say that the grandparents are abusive or negligent. If not, I think you should re-think this.
At the same time, I understand your concerns. I would negotiate something with your in-laws. You could tell them that you feel that three weeks is too long a time period for your children to be away. That's a very reasonable reaction. Could they take a shorter trip? If the children are under ten, they aren't going to travel well long distances in the car. Would the grandparents be willing to rent a cabin on a lake somewhere for a week, to share with the kids? What would make you comfortable about the kids being in the situation of travel/away with their grandparents? I think if you could spell that out to yourself and then to them, you'd have a good chance to work out a relationship that is good for all. You could also share with them how important safety rules are to you and to the kids, and ask for their support. Putting it all in positive terms, they may see where you are coming from and react positively. I hope.
Good luck,
Kathleen