Your son is a very lucky guy!!! I had wanted to do the same for my son his senior year. (He's now 18 as well, but graduated in May and will be 19 in December)but, his senior year wiped us out. Senior pictures, yearbooks, Homecoming dance, winter ball, prom, graduation, graduation gift, invivtations, new car etc. ...... Not to mention his freshman brother!!! OUCH!! Still trying to catch our breath. There is so much for them to do and see. It will be a memory maker for sure. I hope they have a wonderful time. My son thought he died and went to heaven when we took him at 16. Have you thought about getting him dive certified before you go? My son just ached to try diving, but I didn't think about it, and didn't feel comfortable getting a quickie 3 three day cert in a swimming pool. I don't dive, but he was sick he didn't get to learn. Sailing and fishing is wonderful!!!