14th Birthday Ideas?

My birthday is on the 12th of March and I'm looking to have a party with around 20 girls and around 7 lads so there would be between 20-30 people. I would be having it at my house and I would like everyone to be nicely dressed up. I know that it sounds like I already basically have it planned, but I'm worried that it will be boring seeing as the last party we had people went round saying that it was boring. I just want ideas on things that we could do that aren't childish?

By Ash J