I have no experience travelling with infants, so I can't address your situation exactly, but I will add this: I think taking the shuttle over with your whole party from the Rad. to the Port will usually work fine, and I think most people do that. If you are renting a car for the return trip, I would consider sending one person over to pick up the car. It seemed that people were a bit more spread out, coming at different times, the day we got on the ship, but when we got back, there was quite a crowd trying to get on the shuttle back to the Rad. so sending one person might be easier.