D.B.
Well, first: what are 2 20 year olds going to do in Vegas while the parents are in the shows and casinos? And are they going to pay for him to have a separate room? If the family was going to go camping or hiking or on a whale-watching trip to Califrnia or just about ANYTHING ELSE, I might say OK, (after meeting with the parents for a couple of hours without the kids to experience if they are responsible parents who set limits with their own child and get respect). Vegas would not be the place I would OK an underage young man to travel with a young woman. Unless there's a different destination in Vegas they're going to travel for, like a Gem & Mineral Show, and they both like rocks alot. They can stay in Houston or go to Tucson for that, and avoid Vegas.