Being it will be your first time in Las Vegas, 2 or 3 days will be hardly enough time to do and see what you seem to want to do. Five days would be more realistic to do what you would like.
I would skip Hoover Dam, it will take 1/2 day probably. Go downtown at night and see the lightshow starting about 8:30 at night plus the casinos downtown. Staying at the Westward Ho is great, I usually stay there, they have nice rooms, is cheap, you can park in front of your room and the lights at night are magnificient down there.
Westward Ho also has the 3/4 pound hotdog for 99 cents and is the best buy in town plus their 99 cent Margaritas. The best buffet is at Bellagio, about $30 or so but is worth it. The best sportsbook is at the Stardust, but most of the larger hotels all have good ones.
However, like I said, 2 or 3 days is hardly enough time to see this great city and take in the free attractions, etc. If it is at all possible, 5 days would be more realistic to really enjoy and see the great sights since it will be your first time there.
P.S. I love the photo with the kids playing poker or whatever!