Hi Denise!
I think you'll benefit if you plan on experiencing attractions without height requirements. The good news is that the Disney World parks have plenty of those for your family to enjoy! There is a Disney site that I think is helpful
here. It has a pdf with park maps highlighting some great attractions for little ones, and a pdf listing attractions with height requirements.
Make playing in the parks easy on yourself and plan to go at your sons' pace. If necessary, plan to get back to your resort room for a nap. Try to stick to regular eating schedules. Keep some snacks with you just in case. When you are at the parks and getting food from quick counter service locations, cast members can assist you with getting your tray of food to your table. (If help isn't offered, ask the cast member that takes your order so they can have someone come and assist you)
I normally suggest you bring a stroller with you rather than renting one so you will have a stroller at your resort and during your travels, but if you plan to use Disney bus transportation instead of Disney's monorail or water launch, consider how feasible it will be for you to have both your kids, a packed bag, and the task of folding and carrying the stroller and carrying both kids onto the bus. You might actually benefit from stroller renting at the parks, or you may consider driving a car and/or staying at a resort with monorail or water launch transportation.
Get to the parks early so you can enjoy them with the least amount of crowds, especially if you stay at a Disney World resort and can take advantage of Extra Magic Hours.
I hope this helps you plan your magical vacation, and that you find Disney World to be a great place for your family to visit! Come back to the Moms Panel for any additional help!