We've done the Jeep Safari in Cozumel. Booked it privately as we were a sizeable group, but sure it was the same tour.
I dont recall a rain forrest though.
But we had a terrific morning doing that tour. I would think if there's only two of u, they'd just join u up with two others to fill the jeep.
I didnt see any safety concerns. Just buckle in for the off roading, and enjoy the laughs!