Car, golf cart and trailer will weigh too much for a gasser MH towing specs.
If your "have to" set up is to tow all three a DP is going to be your only answer. Or buy one of those real small light weight pick up trucks Like a Canyon or whatever and set it up to tow four down behind the MH and put golf cart in bed. And sell that 28 foot trailer!
Yup there are going to be people who say they do haul a loaded 28 ft. trailer behind their gas MH and that you can too.
But you won't be able to go up any type of hills let alone steep grades with that set up in a gasser. Well technically yes you could go up but at 30mph or less tranny screaming. :W