I'd suggest limiting long sit-down meals to breakfast/brunch (if cost is an issue, since breakfast is usually the cheapest meal at any restaurant), or during dinnertime (after a nap, and an ideal time for everyone if the cost isn't prohibitive), so your child is rested and refreshed. Character meals are high excitement, and pricy, and there's no sense wasting money on a lunchtime meal that carries a higher risk of meltdowns because it's overlapping with the usual nap time.
We typically take a 3-4 hour break in the middle of every Disney day, too (even though the kids are older now and don't nap at home). About an hour of that is spent traveling to/from the hotel. Another 90 minutes is spent napping, and if we can squeeze in a quick dip in the pool with the remaining time, we do so. We find that a daily post-lunch nap at Disney (especially since we're always up early for rope drop arrivals) is an absolute must, regardless of our ages or fitness levels, and keeps all of us cool, recharged, refreshed and happy.