We're going to Disney in a few weeks with DS4 and DS2-renting a car. I would rather avoid taking two carseats along, if it's legal. DS4 is 4, 40 pounds, and 44 inches. We still use one at home that he is about to grow out of- soon we'll have to start using just a booster. Should I buy the booster now and bring it, or do I not need to? I'm worried if he gets a week off of carseats, he'll complain about going back to one at home, and here in VA, I think the law is they have to be in one until age 6.