Your whole family should be eligible for health care and in Canada pre-existing conditions are not excluded so you should have no worries. Ontario used to have a problem with people on open work permits but from what I have heard, they have fixed that issue. There may be a 3 month waiting period to get health care depending on what province you are going to. If your wife manages to work at least 600 hrs. in Canada before giving birth, she will be eligible for EI maternity benefits.