Tara, please don't take to heart what a childless woman once said about child-rearing. Everyone knows that the actuality of Motherhood is totally different from the imagined version. And it's something that you CANNOT know about until you've actually done it.
However, that being said, you can probably expect that this DIL will be pretty possessive of her kids. I don't know if it's a direct result of having tried SO HARD to get them, but a lot of people who struggle with infertility are more possessive / protective of their kids. (And I'm raising my hand here too.) My DD did not spend a single night apart from me until she was 4, when I had to go out of town (she stayed home with Daddy). She spent her first sleepover with my Mom this past summer (at almost 6 y/o).
As for mentioning your other GK's - that's a hard one, because some people who struggle with fertility are really hurt by mention of other people's babies/pregnancies. It never bothered me, however I did have issues with irresponsible teen mom types. As long as you're relaying positive information, funny stories and the like, I don't see it as a problem. But please refrain from comparing the kids, because I can guarantee that she won't want to hear that 'other' gk was walking a 9 mos, when she tells you that hers started walking at 11 mos.
Good luck - I hope that you can usher in a new phase in your relationship with DIL & DS. I can hope that when they become parents, their eyes will open wide.
Hey - have you sent DS some of his baby pictures yet? Or any of his old baby stuff? He and DIL might like to see that stuff and have copies of your pictures. However, only do this if you can send it without expectations of it being used. Again, people who work really hard to have a baby sometimes go overboard with only wanting NEW things for their baby. So maybe put an old outfit of DS's on a teddy bear? Or offer a cradle with the intentions of it being used as a doll cradle?