Travel booster seats?

[LoveItOrListIt]

We are planning a US road trip later this year (SUV) with kids (aged 7 and 9). They both have high back boosters in the car at home although 9 year old at 140cm uses it less and less but likes it for longer journeys as is more comfortable.
we will be on the road quite a lot and trying to figure out best approach. I could hire seats with the car rental but they were extortionate and having hired car seats before when they were younger, they were always a bit grubby! Obviously we can’t take our own as too clunky/liable to get damaged in transit. Was thinking about inflatable booster seats (so convenient for packing) but not sure if it is worth it? Any tips?

I'd probably just take backless boosters, or even buy a couple when you're over there, or get delivered to an amazon locker. If you're buying there, you could even get a high back booster if you want to. The Bubble Bum doesn't offer any more protection than a backless booster anyway, and the rigid ones are shown to be better in crash testing.

Check the state laws where you're going but I expect car seats won't be required in the US in most places at those ages.

There are a couple of foldable high back booster seats, but they are quite expensive and it seems superfluous if you can drive from the airport straight to Target or somewhere and buy car seats.

At the end of the trip, give them to the hire car place or offer to any other family you see coming through or donate them to a thrift store. Or just bring back as spares.