Whilst that may seem like an important perk, especially if home is a 14 hour flight away, J class travel for kids shouldn't be a prime deal breaker for your friend. Overall quality of life (work vs leisure time), education (quality & cost), general living environment, accommodation (location & standard), Company culture (punitive vs Just) route network and time to command should all feature above that. Some may disagree? Either way, a difficult decision for sure.
Sadly, 7 or so years ago it would have been much easier.
Harry