Shame on you refering to the 6 year old as a pet!
All Westin Hotels permit pets--including the Casuarina in LV. Aladdin is part of Starwood (Westin) but they don't take pets. The Westin has gaming but the casino isn't as big as the megaresorts. Plus, since the hotel is smaller (by comparison) you won't have problems finding your way around. Check with
captaincrash for a hotel review.
Marriotts usually don't take pets but most of the Marriott Residence Inns do. The ones in Vegas are non-gaming facilities.
Both the Green Valley Ranch and Red Rock (part of Stations Casinos) take pets. Red Rock also has a Kids' Quest (think
DCL Oceaneer's Lab/Club) on site. We dropped DS1 off there a couple of times while we had dinner or gambled. You don't need to be a hotel guest. But note that if she's going to ever go back after this visit, she'll need her immunization record.