Help... overstayed TWP, CEC PR accepted

Hi there

My husband and I have been living & working in Vancouver for 3 years. We applied for CEC thinking we would get it before our WP expired. Unfortunately it took much longer than the predicted 6 months and we ended up overstaying, thinking that we were on implied status. When we called the immigration number they informed us that we had a grace period of 90 days after the expiry of our WP to submit an extension or change of status. We scrambled to do the necessary advertising for the LMO for our jobs (we have been advertising for two weeks now).

We received the request for our passports and have now received them back with PR visa.

My questions are:

1. Can they activate the PR while we have no legal status in Canada?
2. Will they activate it if we go into the CIC office in Vancouver or should we drive down to the border and reenter?

Don't want to be detained at the border for having overstayed....

What should we do?

Thanks