There's a room in the SK/AC London Lounge at LHR which is meant for families and the TG website describes a children's area in one of their lounges at BKK. I'm hoping to use both of these in the near future.
(hope it hasn't been discontinued, I'll print out the page and pull them up on it if they have -
yep, still advertising a 'kids corner' 20FEB11 )
Not sure what I'll find at NRT or ICN but I've seen mentions of a play area at ICN, not necessarily in the lounge though. I'll be happy to report back. (sorry, using an iPod and the post about ICN just wasn't visible to me)