Personally, I'd only have them in a car seat which offer side protection and has a sturdy structure too it, rather than just a basic booster seat. I plan on keeping the kids in that type of seat until 10yo+.
You also might want to check his weight against government advice for using a booster seat.
https://www.gov.uk/child-car-seats-the-rules
You also might want to check his weight against government advice for using a booster seat.
https://www.gov.uk/child-car-seats-the-rules