POOL PARTY!!!!
I am eleven and had a pool party last year for my birthday, it was a total hit everyone was talking about it for weeks.
It cost under $75.00 all you need is towels pool toys (dive rings floaties etc. )
We played fish tag with a mechanical swimming fish available every where just throw the fake fish in the pool and let it swim tell the kids to not get tagged by the fish if you get tagged your out.This game lasted 40 min. and was very fun.
Instead of tablecloths use beach towels have dive ring contests and do freestyle races.