We found that everyone, including kids, usually just wanted to get the traveling over with and get to the campground. I pretty much always want to take a break every 1 1/2 hours, usually just at a rest stop. Stopping much longer than 15 minutes would just seem to make the trip drag.
When we did stop for an extended period (overnight at a campground on the way to Disney World), the kids actually just wanted to eat, go to sleep, and get up early to get an early start and get there.
You might find that "planning" long stops can just extend travel time longer than you end up wanting.
