Dear Kashifa,
Receiving & Sending the PR cards out-of-country, by a 3rd person, is illegal. However, many do so and is seen as a regular practice. In fact UPS has a 'box service', which they use it for this purpose; and at a certain additional cost also send the cards overseas.
But, the fact remains that it is illegitimate. Morover, if our PR cards are lost in transit, we have no recourse to get them issued again on that pretext. And thus, our re-entry into Canada shall become problematic. Even though we apply for a 'PRTD-A31 (3)' ['Temporary' PR Travel Document] at the local CHC, that might also go into a rigmarole.
The ideal solution is wait for 30 days at Canada, obtain the cards personally and then move out. Else, move out without applying for the PR cards and re-enter Canada with a PRTD; thereafter, apply for the PR cards at a later stage, upon re-entry.
End Note: As stated above, mailing the PR cards overseas is a practice though. So, you may do so but there's a risk, which u shoud be aware of.
HAPPY NEW YEAR !