We have not yet stayed at the fort, but are rending an RV (toy hauler, for the back ramp to add accessibility to it) in a few weeks, and added on a golf cart with the RV rental.
We have a family member who uses a wheelchair, we are getting a golf cart anyhow, because the rest of the family may want to use it to go to the pool, to get food etc. My dad will also likely be using a
scooter. Our thoughts are that even though we won't be able to use it for my daughter to go exploring, the rest of us will benefit from using it. When thinking about logistics, waiting on busses does not sound fun, I remember going to dinner at the fort several years ago and getting there via bus seemed to take forever. We had thoughts of maybe using our vehicle to drop my daughter <and her wheelchair> and my dad <and his scooter> at the boat dock, when using the ferry, then we can swing back and the rest of the family can use the golf cart to get over there, if it's too far from our campsite for us to want to walk
Still not sure how any of this will play out when we get there, but if you think about the cart for your traveling companion(s) vs for yourself, maybe that will help you make a decision. If you were exploring the fort could you tag along with your scooter while they ride the golf cart? (forgive me if that's a dumb question, my dad would be
renting a scooter, I don't know if that would be possible)