Yes all of us have our PR cards and our SIN numbers. No new family members.
Okay. Then the situation is relatively simple, although lacking certainty.
To boil down the answer to brief version but in reverse order:
-if you all arrive and do not have significant issues at border, you should not have any issues in Canada as long as you remain in country. School etc, health care will involve some registration and administrative work (possibly waiting periods for health insurance to kick in). Main wrinkle is travel abroad raises risk of getting reported each time - so best to remain in Canada, not travel or renew PR card, until back in compliance. (Once well settled as you will be with health care etc, living in Canada without PR card also not an issue - some do so for years and years, PR card is not the status).
-By 'significant issues', the primary risk is getting 'reported' at the border for not complying with the residency obligation. That would start process of revoking PR status, subject to appeal. You'd all still be let in and reside in Canada while that is going on, as above. The main issue is the fear of not keeping the status - but actually residing in Canada still fine - but no way to know in advance how appeals might go.
-Getting reported at border/airport: no-one can tell you the chances. You should prepare answer, ideally with some supporting material, about why you did not return to settle earlier (humanitarian and compassionate - why it was somewhat out of your control). Clear intent to return and reside in Canada (i.e. job) helps. Kids and family complexity probably a bit taken into consideration.
-The positive aspect is that anecdotally, it seems they are somewhat lenient (so far) with covid as a reason out of your control. Perhaps not a free pass, but with some explanation. Govt took a strong stance to discourage travel and emphasize risks, so it's not really deniable. (All these things would be looked at on appeal, too)
Given all that, there's more than a small possibility that you'll be waved through with more or less questioning, and nothing more serious in conseqence than a verbal warning and a note on your file. (That leniency may not apply to future border crossings though).
So no-one can guarantee you anything. Returning sooner is still better than later (including for other family members) - relative leniency will not last forever, significant changes to your plans (delays) might very much change your chances. And no-one will say what 'chances' are, but yours is far from the only case, you're not decades out of compliance, and the time period does coincide with covid travel restrictions if you're returning per your plans above.
There are plenty of other threads covering specifics, and some - a few - cases reported where those returning out of compliance have shared their experiences. (Details of circumstances do matter though and we don't know them all)