Help! Im Having A 13th Birthday Party Sleepover!

Ok I`m having a 13th bday party and I need some ideas for games/activities. It is a girls only sleepover with about 10-15 girls. I was hoping on having us sleep in a tent in my backyard(if the weather is good) because there is not enough floor space in my house. I thought og having a luau/beach theme but don`t have any games panned. Also I wanted us to maybe do some water activities or something but I dont have a pool, or maybe a little scavenger hunt in the woods in my backyard. If you have any suggestions that would be great! Thanks