As long as the PR card is valid you can move in and out of Canada. I am still half a year away from meeting my RO and I have traveled in and out of Canada by air without any problems. The problem will arise once the PR card has expired and you are outside Canada. If your PR card expires while living in Canada, it will not pose a problem unless you want to travel. So whoever is travelling into Canada should travel with their VALID PR card and stay till you meet the RO (730 days) and apply for a renewal.
I mostly agree with this but there is one clarification which warrants attention, regarding the effect a valid PR card has.
A valid PR card means the PR can board a flight to Canada.
In contrast, it is having PR status which determines the right (a statutory right, which is often referred to as a "privilege") which allows the PR to actually enter Canada.
Being able to enter Canada is one thing. Potentially being reported as inadmissible, due to a breach of the PR Residency Obligation, is a separate thing. A PR in possession of a valid PR card but who is not in compliance with the PR RO is at risk for being reported upon arrival at a POE. A valid PR card does NOT necessarily mean the PR will be allowed into Canada without being reported.
There is, of course, a bigger risk of a PR RO compliance examination, and being reported, for the PR who does not have a valid PR card when he or she arrives at the POE.
The PR carrying and presenting a valid PR card has good odds of being waived into Canada even if the PR is in breach of the PR RO. But this PR, nonetheless, could be asked questions about compliance and if not in compliance with the PR RO, then reported. Having a valid PR card does not immunize a PR from being reported.
Your anecdotal experience merely illustrates that it can indeed be easier to enter Canada without being reported for a PR with a valid PR card, despite being in breach of the PR RO. It does not mean it will usually work that way, let alone is likely to work that way. PRs with a history of recently coming and going are more likely to get a pass. But the longer the most recent absence, the greater the risk of a PR RO compliance examination and, if in breach, being reported. And again, this can happen even if the PR has a valid PR card.
For the OP's scenario:
Traveling with an immediate family member who is well-settled in Canada may improve the odds of being allowed into Canada without being reported. No guarantee, and actually far from it. But it could make the difference.