How many hours/days do you think you'll have to wait to get a mechanic over from STT? Think about the logistics. I suspect they'll send one person over haul both the vehicle and you back to STT. Better off getting a 4WD on STJ. Have been pleased with Conrad Sutton in Cruz Bay.

Trust me rent with Dependable. Better rates, they pick you up at the air port and drop you off. You get to save ridiculous taxi rates to red hook plus get to stop by Costco for food and liquor. Ferry fees are better and you hit the ground running on St. John. If your new jeep breaks down (this has never happened in my 8 years of St. John) The mechanic on ST. John will come help you get up and running not St. Thomas.

Since you are renting 3 vehicles, have you considered one on STT and using it to pick up deliver your group to the passenger ferry then picking up groceries on STT before driving to the car barge? Your group could pick up the other two jeeps on STJ while you run STT errands.
I use L&L jeep rental on STJ. They meet you at the ferry dock on your arrival and departure. No hassles, no worries, new vehicles. The only thing missing is in town parking. That is not a problem for us as we almost always visit during off season.

We use Discount Car Rental on St Thomas. Rented a Jeep Liberty last year and a Jeep Wrangler Unlimited for this March. We take it over to St John for day trips. Their rates seem reasonable compared to the other rental places that let you take their vehicle to St John.

Dependable has a very good reputation and I recommend them. You can swing into CostULess (not Costco) on Rte 38 en route to the car barge to provision.

We've always rented from dependable on each of our stays. Always been very courteous, reliable response if you've got a problem. Best rates we've seen.

Dependable allow you to take the vehicle over to St. John at your own risk/expense.
Discount Car Rental only allow 4 wheel drive vehicles to go to St. John, but has a machanic on St. John.

Our family has been to St John twice and have rented from Conrads. We rented a villa in Coral Bay and the biggest advantage of Conrad's was that they offered free parking when we visited Cruz Bay or took a ferry to another island for the day.

do yourself a favor and rent on STJ, call Thomas @ Hospitality Vehicle Rental, he is across street from Post Office, then you will always have a place to park and you will appreciate his service.

😎

I would recommend Amalie. We have also rented from Dependable, with no complaint. Prefer Amalie because they BRING the car to the airport, and meet you at the airport upon departure..
No problem bringing the car to STJ.