Each cabin has a a couple of private parking spots in the front (we used one for the car and one for the golf cart). There is also a weatherproof plug in front of one of them that seems intended for the golf cart (I think it may be 220V).
As was mentioned, you can drive around the resort but parking spots are very limited. You're also highly likely to get stuck behind golf carts and drive 20 mph all the time, which can get annoying fast. I'd rather be the one in the golf cart slowing everyone down (they are speed limited to ~20mph) than the one in the car.
A golf cart may not be necessary, especially if your cabin is close to a bus stop. There are internal buses that will drive you around FW and they run quite often. And of course you have the buses/boats that take you to the parks.
We left with the impression that the golf carts were an expensive convenience rather than a necessity, but I would still rent one next time. I justify it mentally as renting 4 OTU points daily at $20/pt... Four points makes it sound a lot cheaper than $75/day

(btw the 6-seaters are $100/day)