What items do you need to keep at your parents' house?

I am trying to figure out what I need to buy for my mother's house. The baby will be there a lot for dinners as well as when she babysits. I am assuming I need a pack and play, car seat (or at least adaptor), high chair, and stuff to change her diaper. What else do you think is necessary?

Thanks!

Re: What items do you need to keep at your parents' house?

My IL's house is grandchildren central.

I never have to bring anything other than clothes and bottles/formula for DD.

She has:
Diapers (in every size for every kid.. there or 8 grandkids)
Wipes
Diaper Cream
Toys
Highchair
She has a pack and play AND crib
bouncy seat (although all the kids are too old for it now)

We don't have a car seat for them since she won't drive with any of the kids, but if your mother is going to be driving your DC around, you just need the base for the car seat.