This is what I took in January... everything but the tripod, monopod, and 400mm lens fit (at the same time!) in the bag.
I ended up using the 400mm lens exactly
zero times. In the future, I might also leave the monopod behind and just carry the tripod.
We had a stroller for my son, who was 21 months old at the time, so the tripod or monopod (only carried one at a time) was left in the bottom. This is an advantage of bringing your own stroller vs renting one of Disney's... (they have no storage.)
I'm guessing that I may have to use the lockers in the future when we don't need a stroller any longer... but I'm not sure.
We often switch parks during the day for one reason or another, so where I am during the day may not be where I need the tripod for when it gets dark. But then, I may use it during the day a few times too, and do some HDR photos.