Middle school graduation dance after party (limo, resturant, partying) help?

Okay so my best friend and I decided to rent a limo to take us from the graduation dance to a restaurant. We are trying to go to a restaurant with a party room or we will call ahead and have them reserve LOTS of space. We are thinking of inviting 20-25 people. Do you think that we should take a hummer type limo or a party bus? I don't know what the costs are around but the limo/party bus is only going to be driving us for like 15-30 minutes. How much do you think it will cost an do you think we are going over board? Oh and is there anything else we can do to make the night more memorable? Thanks a ton and btw we are 14, and popular. I don't know if you really need to know that....xD thanks again(: