The fee shuttle from Doxology on Hulen is great. If you come from McKinney you would just take I-35 to I-20 and take I-20 west to Hulen. The church is about 3/4 a mile north. Parking is free, shuttle is free and takes you right to the stadium. University Baptist and University Christian Churches both have parking for $40 or $50 within a couple blocks of the stadium. Paschal High School at Forest Park and Berry has cheaper parking ($20?) with a free shuttle about 1 mile from the stadium. As someone else said, if you get there early, there are plenty of people who will let you park in their yard pretty close in for between $30-50.
Whatever you do, if you are coming from Dallas or the northern burbs, don't take I-30 to University and go south to TCU. Traffic will suck ass. Same goes for after the game. Avoid that route. Take I-35 to Berry and go west toward TCU.
If you don't mind a little bit of a walk, my suggestion is park at Paschal, walk down to Dutch's and grab a burger, then walk across campus to the stadium and then take the kid to Frog Alley for some pregame bounce house and other kid oriented entertainment. The walk through the campus from Dutch's is nice and the kid will love Frog Alley.