Birthday party theme for my sons?

I want to throw a combine birthday party for my 2 years old daughter and 7 years old son.so what theme should I decide

Maybe a Carnival theme?
Like maybe rent a few Ponies, make Game stands with cheapish wood.

A Carnival is a good idea... maybe you can take them to a place like Jump Zone where it has tons of inflatable games that even your 2 year old can play on.

Luckily, they are at an age where the fact that they are boy/girl doesn't matter! I like the idea of a carnival, or maybe have a petting zoo! Also, you could have a clown come or a puppet show person! hehe there are tons of great ideas!