Tough call! I know what a pita it can be to haul carseats through the airport, especially if it is you alone with 2 kids! I have the radian, and it folds up great for travel, installs like a dream on the plane, and in cars with LATCH, but it is HEAVY - DH and I had to take turns lugging it thru the airport. OTOH, we have travelled with seats like the Alpha Omega and although they are bulkier, not nearly as heavy! In canada evenflo makes a seat called the chase, which is superlight and holds up to 48lbs. I believe same seat in the us is only good to 40lbs though, so your son maybe is too heavy already. If you folded the Radian, and packed it in a suitcase with some clothes around the edges, you could go ahead and check it, and then just get it out of the suitcase when you needed it, which would save you lugging it thru the airport and security etc. It folds small enough to fit in a regular suitcase, and at 30ish lbs, still light enough to allow suitcase to hold some clothes. The vest is a good option too, but not so practical for everyday use (and I have heard nothing good about the tote n go at all, the ridesafer is the only one with decent safety), where at least the Radian would be good for use after. I am a HUGE believer in extended harnessing (hence hauling the radian thru the airport for our 5 year old!), but really, I might be tempted to consider a really good booster - compass makes a really nice one that folds as well, lined with eps foam, nice wings for body and head, that would be super easy to have your son carry on the plane and stow, and then you would only be carrying for the little one.