How much will a trip to Martha's Vineyard cost?

Hey over the summer me and my 3 buds are heading down to the Vineyard. We're all gonna be 16 and 17. 16 bucks round trip on the ferry, plus the $135 to bring the car. Total for that comes out to 50 for all of us. We're staying for 2-3 days and we're not getting a cottage or anything, we're just gonna bum and set up a tent. I'm thinking an extra 100 for some fine dining and an extra 50 for gas/anything else. Do you think 200 sounds reasonable?