If your child does not land before the PR visa expiry, he will not get PR. It will not affect your and your husbands status and you can sponsor your child for PR later.
However, keep in mind that as a PR, you must be residing in Canada in order to sponsor your child. If your child has a visa exempt passport, you can take him with as a visitor when you are ready to move to Canada. If he is not, it starts to get complicated. He would not be issued a TRV (visit visa) because immigration would say that your intention is for him to stay permanently and not to visit. It is possible that you could get another temporary visa for special circumstances called a TRP. This would allow you to take your son with you to Canada to sponsor him. If you can't get that visa, you or your husband would have to go to Canada without your son and reside in Canada without him until the sponsorship goes through. Depending where you are from, sponsoring a family member can take months or even more than a year.