I second the Starwood nomination. Most of the Westin properties have a "kids program" where some may have daily programs (most resorts, not too many business hotels.) If you give the ages of your children, you get an age appropriate ammenity at checkin, and the staff has a "whatever you want, whenever you want it" mentality (not quite as much as the W's, but still...)

Barring that, Embassy suits is great among family travel, because of the extra space. Dont know very much abotu any kids amenities, but my aunt and uncle, with three children, tend to stay there.