15 Year Co-Ed Teenage Birthday Party

Umm, hey . I am turning 15 this summer. Im having a co-ed party (boys and girls) and im starting to get a little frustrated. First off. I dont know who to invite. At school i hang out with two different clics. And some people dont along with the other people. So, i dont know who to invite.second off. Decorations, im not to sure what i should get for decorations, or if i should even have decorations. My party is either going to be at a private beach, or we are going to rent a field and camp. Third off. Activities. I have no idea what to do for that. I havent had a party in about 3 years other last year at my rugby party and that got busted by my dad because someone snuck alcohol to my party (my dad doesnt think its right at my age, unlike other parents). And people are suggesting truth or dare, or seven minutes in heaven, but i dont know if i can play those, because my dad is a little up-tight and is going to be watching everything we do. Since last summer. He doesnt exactly trust me . And like, were getting to old for the little kid games, i need something fun and exciting.UHH I NEED HELP, I DONT KNOW WHAT TO DO !? soo, invite ? decorations ? activities ? help, please. Write back soon .