Disney is just a different situation than normal every day stuff - lol. It also depends who the rest of the group is. If the younger kids have a place to sit for a bit, then you can go longer into the day and keep the older kids happy too. A quick nap in a stroller can also revive even the heartiest 4 year old so he can last till Spectromagic!!!
We were there on New Years Day. It was crowded - I actually felt safer when I was pushing the 4 year old in the stroller - at that height, people just didnt seem to see him (he is a big 4 too) and would just bonk into him!!! He was right at the level of peoples bags and backpacks too - got bonked into walking from Fantasy Land to Tomorrow Land and it knocked him off his feet - thank goodness he is good spirited and I was holding his hand. After that when he was walking with me I felt like I was steering him to push him out in front of me. Once he got tired though, into the stroller he went.
At the end of the day we ended up with a sleeping 2, 4, and 6 year old!! We had 1 umbrella stroller and of course were parked waaaaayyyy at the end of the row!! Bring a stroller - you can always just leave it in your room if you end up not needing it - I have to admit, it is nice though to have it to carry the bags, sweatshirts, snacks etc......but You know your kiddo the best!!