Adopted Special needs son from Canada( Complicated )

Hi
I am an Irish citizen who moved to Canada, I have a common law partner of 5 years with 2 biological Children and 2 Adopted Children.
One adopted child is 18 and special needs.
I would like to apply for them to move home with me but would like to do this from Canada, as I can only imagine the crap I will have to go through when I get home to apply there.

If I have to wait to apply when we land in Ireland what are my immlications for work, can I claim I have 4 children for tax purposes while waiting for approval? What about health coverage while waiting?

ALL Advice is appreciated