Some states allow triple towing (Your TV + Trailer + Trailer).
Others do not.
Some accomplish having the golf cart by having a toyhauler, others by having a bumper pull and hauling the golf cart in the bed of the truck and unloading after disconnecting the TT. I have not seen a 5th wheel with a rack on the back for a golf cart, only class "A" motorcoaches.
It will take a very strong frame and frame mounted system to accomplish what you are looking for. I think it is the most worrisome solution as you likely are going to have to beef up a frame that is/was not designed to handle the stresses of hanging an additional 1000-1500 lbs. off the back of the 5th wheel.
I think either of the other two options (Toyhauler or TT with GC in the bed of the truck) is a safer and better solution.