Theoretically, as the union is considered a legal one in the home country, and the child is legally adopted, also in the home country, I see no reason why the Singapore government would not grant them LTVPs, at least initially. Whether or not they would every be approved for PR is another story though.
I have a strange feeling that the government's magnanimity might not extend quite that far. I don't have any anecdotal evidence to support this, but having been here for a couple of years it makes sense to me, especially if the figures you quoted are correct. If he's been legally married in Canada for two years, I think I'd go for it.
IMHO. (me? humble?)
