Hi Lilly,
I really appreciate that you are asking about planning so that you do not run out of energy. Walt Disney World is an amazing place, and there is so much to do that it is quite possible to get overtired if you do not plan. Let me share a few of my best tips for keeping everyone well-rested on vacation.
First, I suggest that you try to maintain a typical schedule for your children while you are at Walt Disney World. If your one-year-old still naps, try to head back to the resort to take a nap. It might also be good to take a mid-afternoon break with the five-year-old. For your five-year-old, a break might be heading back to your resort to go to the pool. If your park touring will not allow a mid-day break, try to plan some attractions that will allow some down time for your children, such as taking in a show when you know that they could use a break. Also, take advantage of the
Baby Care Centers located at each theme park. They have quiet, calm, air conditioned areas for feeding and changing the little ones.
Since you have members of your traveling party from three generations, I also suggest that you consider splitting up for a while each day. I tend to find that a large traveling party is freshest in the morning - so you can all head to a theme park together in the morning, but then consider splitting up mid-day so that anyone who needs to can take a break. You can get back together again around dinnertime.
Do not underestimate the importance of staying hydrated and well-fed. I always take bottled water and some simple snacks in my backpack to the theme parks. This way, we can stay hydrated and keep our energy up, even if the urge to snack happens while in a queue.
I would love to help you plan more Lilly; however, I am limited in the space that I have to answer. Please do write back if you have any further questions!