Your only real option is the titular Marquette Park. There's also Oakley Park, but it's hardly a real park. Marquette Park itself is very big, nice and clean, and kids can have a great time there.
The best park in Marquette Park is going to be Marquette Park. This park is the largest southwest park in Chicago. There are soccer and baseball fields, and also a 9 hole golf course complete with a lagoon.
