How to make $350 in 3 months?!?

Okay so one of my best friends is moving(out of state) in late july/early august and so me and 3(or 4 if my sister decides to come)other girls who are really close with her are making a plan to have the best summer plans before she moves. We are going on lots of mall trips and ect. we are also going to go to dollywood once she moves(we will stay at her new house). We are gonna go to water parks and go to my beach house and soo much more. but the main thing we are doing is going to Sea Island Georgia. We are staying for 2 nights and one adult has to come. We each have to make $350 to pay for the room. So how can I make $350(or $300) in 3 months without getting a job(not old enough)???