If you're just driving, then take the dry powder, put it in a cooler with ice (but not directly on the ice), bring bac water/syringes and reconstitue at the destination.
You could also reconstitute at home, pre-fill your syringes, and put that on ice (but again, not directly on it).
Reconstituting and leaving it in the vial would be my last option (= most josseling around), but I still don't think it would damage it.
And make sure your destination has a fridge. If not, just get fresh ice each day to refill your cooler.