Hi Althea,
Your daily itinerary will depend on time of year traveling and location of your Resort. If staying at a Disney Resort Hotel, I'd definitely suggest hopping on a bus or monorail for a mid afternoon rest, swim or "re-group." If traveling during hotter months, you may find the hours between 1:00 p.m.-4:00 p.m. to be well worth the rest or swim time.
I always suggest arriving right at Park opening time to be sure you can tackle the most popular attractions in the first hour of the day. For example, when visiting Magic Kingdom, head directly back to New Fantasyland and experience Enchanted Tales With Belle, Under the Sea - Journey of the Little Mermaid and Dumbo the Flying Elephant before the crowds bulk up by mid morning.
My best suggestion would be to check out the
Park Operating Hours. If you're staying at a Disney Resort Hotel, definitely take advantage of Extra Magic Hours. If traveling during off peak months, you may find the Parks closing earlier each evening. You also may find the weather to be quite tolerable for a 7 & 8-year-old and maybe won't need to travel back to the hotel. It's really a personal decision and only you will know the itinerary tolerance of your family!
My kids are 6 & 8 and we still travel back each afternoon for a rest. The Florida sun is much different than our Chicago sun, and I don't think we miss a beat by resting for awhile. It allows the kids to recharge and lay down for a bit so we can stay out late and enjoy the amazing fireworks.
Hope my suggestions helped, Althea. Thanks for visiting!