I want to get my son a trunki for Christmas because we travel long haul about once a year to visit my husbands family, plus smaller trips during summer. He saw a kid on one at the airport a few months ago and kept saying he wanted the "tiger car". But he'll be 4 and a half at Christmas and I swear those things aren't that big! Does anyone have one? Can you recommend? How big/old does a kid have to be to stop being able to ride on one? And are they accepted as cabin baggage/how much fits in? TIA!