Since you are taking a 10 year old, I would definately stay at MGM Grand. It is huge, but has many kid friendly things to do. Plus their pool is the best, with a lazy river and many pools, one of which is just an adult pool!
Vegas has changed in the past 5 years or so, not so family friendly as it once was.
We are headed there in a little over a week and I'll post some photos for you. There is a Rainforest Cafe in the hotel, plus easy walking to NYNY, Excalibur and Luxor. I would not stay at Mirage, Bellagio, Wynn, Venetian or any of the old school places, Ballys, Flamingo, Tropicana. Also skip Circus Circus, not nice anymore!!