I tow a 22' trailer with UTV and small SUV and I am in a similar dilemma as you...trying to reduce tongue weight.
You have a Smart car at 2000 lbs, an ATV at 500 lbs, and a UTV at 1200 lbs. I bet having the Smart car in the front puts you over the tongue rated capacity.
Without using a WDH, I'm guessing that the only way to get your tongue weight down to the hitch rating of 750 lbs is to put the Smart car in the rear facing backwards so that the engine is behind the axles, the UTV ahead of the car so that the UTV engine is over the axles, and the ATV in the front.
The only way to know for sure is to weigh it. I bought a Sherline tongue scale for about a $120 online and it is well worth it. I would really recommend getting one as it takes all the guess work out of loading properly.