The Character sheet looks fine to me, I can't think of anything else that would really need to be added, personally. As for the plot, the mysterious island thing is cool. I think either starting them at a summer camp or having them already be an established friend group would work best for the plot...maybe we could do some sort of treasure hunt? Mysterious island with treasure? Child pirates? lmaooo honestly, we could go so many different directions with this and all of them sound fun. We could go supernatural and do some ghost hunting, we could go urban legend...so many options.