Good, he doesn't need a Temporary Visa then, (
http://www.cic.gc.ca/english/visit/visas.asp ).
Depending on the ability to prove his intention to leave Canada after the alleged visit stay (6 months maximum, so do not pop saying something like were coming and his gonan be visiting for 3 years). For example he you guys do not even need to prove he will leave after the 6 months, basically one needs to prove the intention to return to home country after the whatever-period-of-time one says will be around for a visit (and you do not need to tell you are going to extend his stay at this stage, but NEED to satisfy the Visa Officer that he will be leaving after).
SO, if you guys will say ok, he's here for 90 days, after that we both, or he alone will be returning to Ireland, show return tickets (If applicable), letter from employer, property deeds on home country, family liens besides you, money to support the amount of time you are saying he is going to stay, etc.
All in all, he shouldn't have any problems at all to stay around in Canada provided you guys can SATISFY the VO, and remember its one's duty to satisfy them, we do not have the right to enter Canada freely as citizens do, even if entering along a citizen, just do your homework and prepare for it.