Karan asks, "While the US Embassy approved the renewal of my H1B, they put my wife and children's H-4 visas in administrative processing and she is stuck in India. They all have valid visitor visas. Could they all come to the US using those while the H4 is being processed?"
The answer is No. Actually, they do not have a valid tourist visa because at any given time you can only be under one valid visa category even if your visa shows a date into the future. When you put your family into the H category they are no longer eligible to enter in the B category unless you specifically withdraw the H petition (at that point if there is still time left on the B visa, it can be used).
In your case it seems that while they maybe able to leave Canada with the B visas (the airline agent will not know that they are under admin processing for H4), they might be denied entry into the US because the H4 is still being processed and the officer may conclude that their intent is definitely not sightseeing. The record in the USCIS database will prove that it is joining you and continuing their American life. You should tell them to wait till the decision is made.