My just turned 3 DD has recently been very sick on 2 longish car journeys. Although from what I've read watching an iPad is a no no to prevent such episodes. It has been the 2 times she has not been watching it (we strap it to the back of the seat in front for watching films) that she has been sick.
Probably answering my own question and if it works, she'll just need the iPad for every journey but other suggestions welcome.
I can't put her car seat in the middle as only have a Golf and a baby seat also. It's not always practical to travel at night.