We just returned from the FW cabins!! I soooo love them!
However we did not rent a golf cart but I can tell you they are $63.54 a night and that is NOT a 24 hr period. I had asked when we checked in, was hoping to rent a cart from the afternoon until the next afternoon, doesn't work that way, would have to pay for another day if we wanted to do that, (it's really by the night like the room/cabin).
We always rented them during our previous stay but I needed to be a little frugal with this trip which worked out just fine. There were plenty available if I did want one at check-in without reserving it ahead of time. I'm sure it depends on the time of year as this is still off-peak. But, if you want to reserve one now for April I'm sure you'll be fine. They are fun to have, but just adds a fairly large amount onto the nightly rate if you think about it that way. The bus system worked fine for us but we missed our scenic cart rides through the loops.