Summer Kickoff Party Ideas?

I know it's early, but I'm planning a summer kickoff party. My parents are a little iffy about parties, so I want to ask them ahead of time. I think they will say yes though because we will be staying out of their way instead of running around the house. Anyways, the last day of school will be a half day, so we will get home at around 12:15-12:30, then the party will start at 3. (Or around 3 depending on what my parents say) We will probably have a waterballoon fight and toss around a beachball or whatever. But I need more ideas for activities and stuff we can do. (By the way we're all 13.) I will probably invite like 8 of my closest friends. Then we will have a barbecue with hot dogs, hamburgers, and maybe some watermelon. Then we might watch a chick flick of some sort because one of my best friends have a huge movie projector, so it would be really cool if we could borrow it and project it on the side of my house. Then we will have a campfire, tell scary stories, roast marshmellows and make smores, and we will camp out in my backyard with our huge tent. (We have woods and a big yard so I'm just going to put the tent close to the woods but not in them because of all the ticks and such) Anyways, I need some ideas of stuff to do to make it a good party, and a good chick flick we could watch. Thanks for any help! :D