Flagstaff Parks: Thorpe Park

Thorpe park (191 N. Thorpe Rd) is a massive Flagstaff park near downtown and Lowell Observatory with lots of amenities. It has two playgrounds, one of which is aimed at the 2-5 year old crowd, the other for five plus... plus two sets of swing sets, including lots of baby seat swings... plus a jungle gym type firetruck for climbing on and plenty of space for running around. There's also a section with lots of ride-ons of dinosaurs and such.
Add to that, Thorpe has several tennis courts, a sand volleyball court, basketball court, soccer fields, youth baseball fields, adult softball fields, a picnic ramada and picnic tables with grills,  racquetball courts, horseshoe courts a disc golf course, a dog park and thankfully portable and permanent restrooms.
It's a fun park that you can always expect to find other kids to play with while you're there.