I think I already know the answer to this question but I'm going to through this out there anyway. We are going to Kauai on Monday. I have a mini-van and a compact reserved (the 2nd car is for my husband to go to work while the rest of us play). My 18 year old would love to be able to drive but most companies state that the 2nd driver must be 25. Some have a surcharge for 21. Are there any companies that would allow my 18 year old to drive? Probably not.... but I told my son I would at least ask.