For charges that are 1 and 2, I'd make sure MB/DB pack empty sippy cups in the carry on. Once you get through security, you can then buy bottled water if they get thirsty. Drinking during take off and landing will also help their ears to pop less (the swallowing helps).
Since there is only one car, how will you get around when you aren't needed? Or is it a resort type place where you can walk to different things? Not trying to pry, just trying to get a better idea so I can be more helpful.
If the flights are not direct, make sure you have a few extra diapers/wipes/snacks. Just in case the layover takes longer than anticipated.