Hi Victoria!
My family almost always takes an afternoon nap break back at our Resort, including when we have stayed off property so I definitely think you should have enough time.
We generally wake very early, eat breakfast at our hotel and get to the Parks at opening time. We eat lunch at 11:30 to Noon and leave immediately after for our break. Generally, we come back to the Park about 3pm where we get to enjoy the evening hours, dinner, and the all important fireworks show without being crazy exhausted!
An afternoon break makes all the difference in everyone's energy levels! I also burn easily and leaving during those peak sun burn hours is better for my skin!
If your hotel is very close by it might take you about thirty minutes to get back. This will depend on so many things, including if you are taking their transportation or your own car. And if you are in your car then how far out you had to park that day. If you are taking your hotel's transportation, ask them how many stops they make when picking up and how long it takes them to get back to the hotel so that you have a better idea of how much time to plan.
Thanks so much for thinking of the Disney Moms Panel when you had a question, please let us know if we can help again.