Unless you know the exact suburb that you'll be settling into, (most people don't 'til they get here) there's not much you can do. Your five year old will go to whichever school is in the catchment area, for your address, unless you pay privately, and then you can choose which suits your pocket etc.
You may need to shop around for childcare for the baby, as in some areas it's quite hard to find. For instance in Sydney, where a huge proportion of mothers work, the baby's name is put on several waiting lists, at birth. Every state differs though, so you might not have a problem.