Vegas in general is not kid friendly but you can easily have 2-3 days of fun with the kids.
You could probably spend a whole day at Circus Circus, they are the only kid friendly hotel and have live circus acts and also have a 5 acre indoor theme park called Adventuredome.
The Stratosphere also has rides on top of it, but 1000 ft up they are probably to intense for the kids, they also have an observation deck that is pretty cool.
Mandalay Bay has Shark Reef, a massive walk through aquarium that is really cool.
You could make a trip to Hoover Dam and take the Dam tour for an educational outing. Even if you don't do the tour the Dam is pretty amazing.
You could also check out Discovery Childrens Museum, Vegas isn't much for museums but this is actually a great kids museum with tons of interactive exhibits.
The Bellagio fountains are a must see, as is the conservatory.
The Venetian has gondolas and a huge mall themed to Venice.
Caesars Palace has the forum shops.
The Mirage has a volcano show.
Treasure Island has a pirate show out front but it's adult themed though with a crew of guys on one ship being seduced by scantily clad women on another ship.
We finally have a water park again (Wet and Wild) but it's in the suburbs, it opened this summer and has been a huge hit.
That's all I can think of off the top of my head, but I think that's plenty for a couple days, just remember the kids won't be allowed to hang out anywhere with gambling or alcohol (other than restaurants).