So to answer your other question, cart rentals are for a 24hr period. Meaning, if you pick it up at say, noon, you have to turn it in the next day by the check in time. I think it was 10:00am but I don't remember exactly. If you picked it up at 4:00pm, still has to be back by 10:00am the following day.
You can turn the cart in when you leave, example 8:00pm on the same day you picked it up, but you still pay the $67 rental fee for the day regardless. I used to do it when friends came down to visit at Christmas time. Rent the cart for the day. Hopefully pick it up around 10:00 but 1:00 was the official time. Sometimes it worked out, sometimes it didn't. Run over to P&js for a quick lunch. Park the cart there, get on the boat to MK and Monorail the resorts. Finish, return to the Fort. Dinner at Trail's End. Then loop and look at decorations till late into the evening. Turn in the cart, keys in the drop box and head home!
Sounds fun huh!
As others have said, carts are reserved for fort guests now. At least Halloween and Christmas. They recently added a bunch of carts to the fleet so there's a lot more to go around. Might be worth a call to see what's been reserved for the day you want to go. Disney doesn't like to leave money on the table so they might rent one if it's available (might). You would still be on the hook for the full day rental so no renting by the hour. No more Trail's End so even if they still rented to non Fort guests we wouldn't go back.