We went to a place called Bear Lake two weekends in a row because it was so much fun.  It is about an hour and a half away and sits on the border of Utah and Idaho.  The water is so warm and the sand feels more like mud when its underwater. It is shallow for a mile, so it seems, that you don't worry to much about the kids, and there are mountains all around. Laura and I had fun reading our Twilight books while the kids turned uncle Seth into the mud monster.