Playroom revisited

Ok, so scrap the dining room idea. I just found out that my mother-in-law (who will be staying with us for a while sometime in the near future) is going to be bringing out a really nice dining room set. Her mother is giving it to her, on the condition that it becomes a family heirloom. Chad said it was bought in the 60's and Grandmother bought it because it was just like her mother's set. I think it will be so cool to have that in our house for a while! Oh, and Mary (Mother-in-Law) is having her stuff trucked up with my dad in July when he comes out with a boatload of stuff for Jay and I from my folks' house. So it'll be taking up residence right away.
So.... the question now becomes, do I let the office be the toy room or my craft room? Do I try to keep the kids' stuff mostly to their rooms? or will I just end up giving them the living room? Maybe I should design the living room with that in mind from the get-go and then it won't feel like the kids are taking over later? I will have the library to be all nice and clean and serene and everything, right?