Hi realpatt, we had your situation, relatives live in Vegas and we were going to visit them with the kids but needed our own place and wanted a kitchen and a nice pool for the kids. We stayed at the Cancun resort in March 2004 and were very happy. First, we had requested a one bedroom exchange and had no problem matching for the week we requested (our spring break) and we were actually given a two bedroom but only charged points for the one bedroom (which was great because the points we saved helped us cruise on points this spring break). The unit was very nice, I wouldn't say its quite as nice a BCV, our home resort and the only one we have stayed at, but it was well furnished, clean and spacious. There was a large, very nice pool with a pyramid and some planted areas which we spent a few days at, and a poolside restaurant we enjoyed for quick lunches. The weather isn't necessarily hot in Vegas in March but we were lucky, so although normally only a smaller portion of the pool would have been open part of our stay they ended up opening the whole pool, the pool schedule might merit checking into before booking if your kids are big swimmers. I think that there were some activities available but we really didn't participate. It is definitely removed from the strip/downtown, not a problem for us since we borrowed a relatives' car, you will definitely need a car if you stay there. For us, it was really nice to have a "normal" place to spend time with the kids away from the casinos and seediness (you are sorry that your kids can read when you see the billboards!)
We have been to Vegas several times with our kids. Good shows for kids: Cirque du Soleil the oldest one I think Mystere at Treasure Island (not O, which is phenomenal for adults and probably teens but I don't think would draw the attention of younger kids, or Zumanity, which is really only for adults); Lance Burton magic show at the Monte Carlo--he is very kid friendly, even draws kids from the audience to help with tricks, we were probably in the fourth or fifth row and my daughter was called on stage to help him and another child with a trick, got a signed poster to bring home as a souvenir); Knights dinner show at Excalibur (a little cheesy for adults, but my son who was almost 6 at the time still talks about it and wants to go back). Attractions: Parade in the Sky at the Rio, fountains at the Bellagio, gardens and Monet exhibit I think also at the Bellagio (daughter then 8 is into art and loved the exhibit), Circus Circus casino indoor circus/ride area, Ethel M chocolate factory tour, and just checking out all of the elaborate decorations and themes at the casinos on the strip!
Sorry so long, and a little late to respond, but hope this is helpful, feel free to pm me if you have any specific questions. We would definitely stay at the Cancun again.