I think I'm one of the few people I know that still has my 5yo-8mo child in a 5-point harness carseat that he's had since infancy! He is fine in his Britax Marathon, but it's time to move on. We will be flying next month, going to the Caribbean, and thought it would be easier to bring a booster on the plane & van; however, the boosters mostly seem to work with shoulder belts and, yet, planes are all lap belts, I believe (have not flown in 5+ years). DS is about 40lbs and is 43 3/4 inches tall (I'd have to double check if it's too close to what the restrictions are).

Do we go with no seat or bring the Marathon(ugh) or something else? Hard to weigh safety vs convenience!

Thanks!
Michele