I agree that Gage Park is the best of the two for kids.
Gage Park also has a great swimming pool which offers swimming lessons for children in the summer. In addition they also have day camps for the kids in the summer.
There are only two parks in Gage Park, Senka Park and Gage Park, and I'd say Gage Park is better for kids. There are basketball courts, baseball diamonds and plenty of stuff for kids.