I saw your post in the other thread too. Just letting you know there are also defence playgroups at all the bases that you are welcome to go too. Check out the following page and click on the NT link for more info or feel free to PM me if you want to know anything else.
http://www.defence.gov.au/dco/community_groups.htm

I also have an 18 month old son and gave birth to my second son last week.