I just realized this morning that since we are renting a car for one day, we will need to bring DDs carseat. How does this work exactly? She is going to be a lap child but I can check at the desk before we leave to see if it is a full flight and if not use her carseat on the plane? If we decide to not go that route, do we use it as a piece of checked luggage or can we gate check it (we will be gate checking the stroller)? Sometimes I am amazed that I have made it almost 2 years, never once forgetting the child while still managing all the gear...