So we are thinking about flying to Florida to go to Disney. We will be staying in a house with some friends so we would need car seats for the kids. If we fly it will most likely be southwest because I can get the best deal on tickets for 4 with them. DS is 7.5 and riding in a booster so I was just planning on packing a backless for him in one of the suitcases. DD is 3.5 and FFing in a TF Roundabout50 and a Nautilus. What seat would you take for her? She rides in the TF in my car, the roundabout in my MIL's car and she rarely rides with DH but when she does it is in the Nautilus. Also would you put your 7.5 year old DS in a backless if he normally rides in a high back booster daily?