Also, since me and my husband continues to remain as PR as we fulfill the Residency Obligation, how/ when can we get our child back to PR status?
Several important points that are undisputed facts:
1) PR status does not 'expire.' Even if out of compliance with the residency obligation, a PR remains a PR (whether one has a valid PR card or not) until PR status is formally revoked or renounced. Your child remains a PR.
2) The PR card is not the PR status, but in your case - wanting to travel back for an important ceremony - it will play a crucial role in allowing the boy to board the airplane to return to Canada.
3) Also indisputable: if a PR returns to Canada and presents at a port of entry (i.e. the passport desk at the airport n Canada), the PR
must be admitted.
Now where it gets uncertain is whether the boy will be admitted by simply being waved through, or warned to be careful about the residency oblgiation, or 'reported' for not being compliant. (That last, being reported, is a longer separate topic I don't wish to go into because I believe it will just confuse things for now - suffice to say even the worst case scenario - he loses PR status but is in Canada - is not that bad as he could be sponsored anew, and I really, really doubt that worst case scenario would come to pass).
Suffice to say, as I wrote above: I believe the chances are
low that there will be no issue on return. And for the reasons I wrote above: you have reasons (covid), he's only a bit out of compliance, he's a minor with parents who are in compliance, etc., etc. I cannot guarantee there will be no issue, but
Two simple conclusions with warnings/caveats: it is really importnat that he return to Canada while his PR card is still valid. And two, there are zero issues with residing in Canada with an expired PR card (nothing illegal about it), just wait until he is in compliance again before applying to renew the card. (That might make travel abroad inadvisable for him for a few months).
I commend you for checking carefully in advance - but if you follow the basics above, you should all be fine.