V.S.
Hi, I didn't have any specific activities for my daughter's party. It was outside and the babies just played with a few toys on a blanket in the grass. Does your party room have a hard linoleum floor? Maybe it would be a good idea to have some kind of mat for them to play on. And put down a few non-porous toys.
My other advice is to keep the party short - like two hours. And make sure your baby has been fed and had a nap. And bring a stroller or pack n play in case someone gets cranky and needs a nap. Have some finger foods for them too. Have fun!