My DD will be 6 by the time we travel. I don't think we've used a stroller in at least 2.5 years, maybe more, at home. We don't even own one.
I think we are going to play it by ear and will rent a stroller at the park if/when it is needed. I suspect we'll be able to tour in the morning and into the early afternoon without one, but by mid-afternoon it could be necessary. Or maybe not, DD did a pretty full day at Hershey Park almost 2 years ago and I think she was in better shape at the end of the day than DH and I were! But that was a single day, not day after day after day.
If we wind up needing a stroller every day, yes it's more expensive to rent it in the park than arranging a rental for the week. But if it turns out we only need it certain days, cost-wise we may come out ahead. Plus we'll only have the hassle of dealing with the stroller for part of the day (afternoon into evening). If she's in the stroller for the afternoon and evening, in theory she should have enough energy to walk from the exit to the bus/boat stop and then from the hotel lobby to our room under her own power.
So long story short, if you are leaning towards thinking you won't need one...at least be open to the potential of renting one in the park on an as-needed basis if it turns out your child could use one after all.