I’ve never seen a golf cart with seat belts so I’d be shocked if they could hold car seats. If anything it makes me think the car seat would be tippy and out the child in more danger.
Possibly Ft Wilderness carts are different from other places?
I don't think so. As @scrappinginontario said, I've never seen a seatbelt or another way to fasten a car seat. I've only ever seen kids that young on a parent's lap while riding in a golf cart.
Yeah, this. There are no seatbelts in the Disney rental carts, therefore no way to secure them unless you're MacGuyver. I live in an over 55 community with lots of golf carts. There are carts that have belts, but they're lap belts only. If you really, really need belts you might check with one of the off-site vendors.