2nd Birthday Party Ideas?

My son's 2nd birthday is coming up in September. We live in Texas so you can only imagine how terribly hot it is down here. We live in an apartment so I really can't invite all the family over at once to celebrate. there is no room, and it is too hot to do anything outside (I tried that out last year, it was terrible!)

So if anyone has any suggestions as to a non-expensive idea for the party I would greatly appreciate any input.
Thank you.

By Shandy