I just asked my 10-year-old son where you should go and he said here: https://coopdevillepgh.com/

We've only ever gone there at brunch time (like 11 or so) so I don't know what the crowd situation there is (it's in the Strip) so maybe other people can tell you what the best time to go would be. I can tell you that I brought five kids there, let them spend all they wanted on video games, and we only spent $100 (not including food), so it's pretty cheap.

Edited because that website sucks. It's a fried chicken and vintage video game place.