Tee Times has been my choice in the past. Last two trips we just used bikes, but Kenny has always taken good care of us. I've seen others post bad experiences but that's gonna be the case with anyone. Tee Times is the only one I've tried so I can't give comparison.
You use their website to reserve. You'll have to meet them off site to get cart. When last I did it the meet was about a mile of Disney property, used their truck and trailer to bring it in and returned it the same way. Took about an hour start to finish for swap out.