In a previous thread, the OP indicated this was four families (kids aged 4-10) headed to family camp at Montecito Sequoia. They had previously looked at a couple of different routes with one overnight stopover and had asked about things like rafting/floating if they used the inland route. There were a couple of river and water park ideas posted on that thread.
Since it now appears the group is leaning toward using 99 with possibly a stop overnight, I thought I'd add a few child oriented stops to consider depending upon the interest of the group to go with the river/water park ideas.
Bugseum - located in Shafter, off Highway 99 just north of Bakersfield. Hands-on insect museum with a kid orientation, gives just a little of the ick factor.
ImagineU - in downtown Visalia. A nice children's museum, its currently in a temporary location while a new 13,000 sq ft building is constructed.
Sierra Cat Haven - located on Highway 180 between Fresno and Grant Grove. (can't forget this since it is bw92116's favorite stop!) This is a park dedicated to the preservation of several large wild cat species. Open 10am to 5pm (last tour at 4) every day but Tuesdays.