L.I.
We love going to the Pop in play times at Pump it up. We also love the kid play times at WOGA gymnastics - its in Dallas though. The movies Cinemark, AMC, Studio Movie Grill all have cheap $1 movies for the kids during the summer. Sometimes its fun and cheap just to go to a McDonalds and let them play on the indoor play area and get $1 sundaes. The museum of Nature and Science has lots going on and has the IMAX and the planetarium, There are also lots of kids activites at the Dallas Museum of Art - I would just look at their websites.
For the area you are in I would for sure check out the website http://www.aroundtownkids.com - they have tons of ideas of things to do all in the Frisco/Allen/Plano/McKinney areas.
Have fun!!