I have 7 kids, spaced 2 years apart. For the last 20 years, we would ususally be travelling with an infant.
In short, most rides can be done with an infant. Our group would typically start together, do rides we can all do as a family. A tradition for us is our first ride is always Peter Pan for example.
Then we would have a nice lunch together, as a group, then split up. The older kids can do whatever they like. The parents, with the infants, at a slower pace. Swapping as needed. Rider swaps seem confusing at first, but once you do a couple, its an easy process. Then meet at the room for a nice dinner, regroup, etc.
When the infant naps, thats our chance for some shopping, etc, see all the "boring things". lol
Pack carefully, spare pacifier, bottles, etc. But every park has baby stuff near first aid, so dont stress. Have a stroller that is easy and quick to fold, to avoid the icy stares you will get on the bus.
One old trick we used to do was when the infant was napping, I'd use that opportunity to wait in a long character line. When I got close to the character, I'd send out a text to the kids to let them know if they want a character meet with no line, meet me at so and so. Sure, a little uncool.... but we don't hog the characters.