We went to WDW last year with our 2 1/12 year old and my experience says toddlers cannot do a full day at the park without a break, so plan accordingly.
You may consider taking a nap brake after lunch depending on how long it takes you to go and come back, we decided it was not worth it. We did either rope-drop until 3 pm or afternoon until late, but this depends on how you like to do the parks. DS never made it to any firework, so a stroller to nap is key specially if you are doing
MNSSHP.
This are the things that we learned on our last trip. I apologize in advance but this will turn your trip into a very toddler centric one, sadly you cannot reason with a toddler so it is better if you just plan around them:
-Have a stroller that fully reclines and add a sunshade if the stroller does not come with a good one. That way they can nap if they get tired and be out of the sun
-book at least one character meal early in your trip, so they can get to know one of them in a more relaxed setting
- Use the swap passes (one person rides and the other waits with the little ones, then a second one swaps with no wait).
- Look at the kid menus ahead of time to make sure they have something the little ones will eat and if not pack something or find out if they can make something they will eat (like a PB&J), the restaurants in the park can accommodate a lot of special requests.
- Forget about bedtimes. Let them sleep in the stroller and go to bed in the resort when you do. This does not mean you don't take an afternoon break, toddlers may need that break even if they don't nap, specially if it is very hot.
- Use the baby centers. They are quiet, you can change diapers (they also have pottys) watch a movie, have snacks,etc... This are good places to take a break if you don't want to go back to the resort. They also have AC!
- Make sure you have plenty of drinks and snacks on hand (this is good for everyone, but you want to have the snacks the toddlers actually eat), a stroller cooler bag was one of the best things we got to take to our WDW trip.
-related to above, get anything the toddlers may need shipped to your room before hand (diapers/pull ups, wipes, snacks, milk in a box that you don't need to refrigerate!). This is a good suggestion for things everyone will need, like water and snacks, but kid's stuff is harder to get on a random supermarket. I had a big shipment from
amazon waiting at check-in.
Since you have a large party you may consider splitting toddler duty sometimes (one person takes the toddlers for an afternoon break while tht others do rides), or even hiring a babysitter for from Disney a couple of times if the kids are flexible enough to accept it. Have fun!