C.C.
At this age they will have more fun just playing with the toys, your bouncy balls, things like that. They are too young for the organized activities that are done at typical birthday parties -- at this point the party is more for the adults than the children!! And I don't know if planning for more than an hour or so for the whole thing will work out: at this age that is a very very long time!
Have fun!!! and don't expect too much -- she is still only a baby, and won't really be ready for the social graces of being the birthday girl for another year or two.