Planning a Party

Lizzy is turning three June 28th. I realize I have a few weeks to plan, but it doesn't hurt to get started. I could reserve the Cultural Hall, since we probably still won't have our house by then. Or I could ask Carrie if we could borrow her back yard again and have a slip n' slide/barbecue party. Hmmm...and then there's the cake. She wants a Sponge Bob cake. Not very girlie but would go with the water party theme. If I don't have an out door party then what kind of games would be fun for this age group? Any ideas would be welcome.