The first 5 years after we bought our MH, we towed our 96 RAV4 2wd on a dolly with electric brakes. Our RAV4 could not be towed 4 down and we could not justify buying another vehicle to tow. I have no complaints from using a dolly. I could load it and tie it down in less than 10 min. I installed a trailer hitch on the back of the RAV and towed the dolly to our campsite.
To setup a dinghy can run around $2400 if all new items are purchased and installed. Even if you install everything yourself the total parts will exceed a dolly w/brakes. I sold my dolly after 5 years use and one new set of tires for $350 less than I paid for it and do not regret towing a dolly for that time.
For your infrequent use buy a dolly and enjoy the lower costs, IMO.