My kids 3 and 7 happily fly business and first, they know the routine and watch movies or sleep. The youngest still can be nervous in some of the newer business seats such as club world if he can't see his parents, but doesn't make a fuss. My employer pay most of these business or first flights so I happily accept. We have also flown economy with them and the experience for the kids is much the same.

Now brats, drunks or antisocial people in any form of public transport are a nightmare.