What would you do at a soon-to-be-thirteen year old's party?!
Answers: My cousin is turning 13 soon and he wants me to help him with games and stuff. I don't do parties well and I don't know what would be fun yet cool. Please help
Have the kids bring multiple game systems and have video game contests. A lot of kids like a "casino night" where they can play poker, roulette, etc. and have them win prizes instead of gambling. Depending on where you live, outdoor volleyball is always fun. Get a scary movie and have the kids re-inact it for prizes. You need to know the kids to know what they like and go from there.
A water-balloon fight?
horror movie?
twister!
^___^