They are over 21, well the gambling floors are. But there is lots to do, loads of shows to see some of which would be suitable for that age group, the strip itself is something to behold at night its so surreal. While there are no major league teams in Vegas maybe you could see a game at UNLV or a non-major league baseball team dependent on the time of year you travel. There are a lot of attractions to be seen outside the city, you could take a trip to the Grand Canyon either by rafting through it, flying or driving, the desert is amazing, there is the Hoover Dam, Lake Mead...