BEFORE THEY CAN MOVE!!!!!
everything is much harder when they are mobile.... when they are young they can go in a sling, or in a pram, or on the floor and they won't move... once they are crawling they are a LOT less happier to be sitting in a pram for any length of time etc...

we have a holiday planned in march where bubs will be about 6-8 weeks.... we also went overseas with our dd who was 2 at the time and it was hard....

good luck, book it soon!