Don't know about Canada, but in the US it is fine. The user manual shows the hook up of forward and rear facing seats in the front seat. There is no air bag in the 1996 XE King Cab that I purchased just recently which makes it ok t use a carseat or booster. My 3 yo son and 5 yo daughter love riding in the front seat, and I use a Graco Turbo booster. YMMV but it works for me, and I have no fear that they are not safe there.
What does your Canadian owners manual show?
For what it's worth, I installed a child seat on the front passenger seat. It was in the 06 Pathfinder w/airbag. I had to move the seat all the way back as possible. The sensor on the seat detected a non adult weight sitting so it turned the airbag off.The CDN manual shows the same... I just wanted some re-assurance from a parent and fellow XE King cab owner.