As a parent who frequently travels with kids, I LOVE the lounges with kids areas and my kids prefer them too. That said, although there is now a kids area in the Syd Int bus lounge, there isn't one in the J lounge and I have one little wanna be WP, so we go in there. The girls in the spa were nice enough to paint my 6yr old's nails last week and it was one of the highlights of her whole trip. They must get a few kids in there though, as there was even a kids menu...
I think kids room's, with electronic games (maybe the could be borrowed from the front desk and boarding passes or passports held as security) TV - with choice of TV programs/movies etc would keep the kids out of the main lounge and make things easier for the parents too, as well as keep the kids away from everyone else in the lounge. Win for everyone!