Las Vegas if you don't gamble?

I will second Valley of Fire State Park and Hoover Dam. Also the Fremont Street Experience - the Viva Vision show is the world's largest video screen (two blocks long) complete with zip lines. The Mob Museum is also interesting and worth a look. In that same neighborhood is the Neon Museum. Vintage signs from "old Vegas", very cool at night when some are lit.

The fountain show at the Bellagio and the indoor canal at the Venetian are also worth seeing. There are also some good buffets if you like to eat (a lot).

Safe travels.