Looks like Laos is out. We would love to see Luang Praban but apart from that there is not much do do with kids except maybe the capital, Vientiane. Roads are a mess, and most of the cool things involve trekking, which isn't something we can really do until the children are a bit older. There was an aeroplane accident a couple of months ago but apparently it was the first in a long time, air safety is not too bad. But flights are expensive and not worth it just to see a couple of things.
We would like to stay a few extra nights up North in Lampang but that means changing a flight and giving up on Ko Chang as we'd run out of time on our Visa. In any case it looks easy to get to Ko Chang later from Cambodia. We'll see what they say at Bangkok airport.