Can't say which is the best, but MGM Grand is certainly one to consider. We stayed there last summer with our kids - 10 &14. They have large rooms and several pools including a river pool with a current that was pretty cool. Rates were reasonable and there were lots of families. If you go there, be sure to check out the lion exhibit there & the free bird show at the hotel across the street (I think the Tropicana).

The Chicago Tribune did a review (with the assistance of a 9-year-old) to rank the best pools in Vegas. Flamingo won. It should be in the archives on chicagotribune.com.

HTH,
Racy

Would not recommend the Aladdin - while of high quality, the pool area and rooms are on the small side and I did not sense any marketing toward children. NYNY has a superior arcade and is across the street from Gameworks. Larger standard rooms are offered at Bally's (mid-strip) and MGM (another good choice for child-bringers, as the pool area is huge and there are many visual attractions. they have (or did have) a good arcade). As a general rule however, Vegas is "down-sizing" its marketing to families. MGM closed its amusement park, TI closed its arcade, and property owners know gambling (meaning age 21+) is where the action (and money) is.