Finally I came back to USA using AVR after completing my landing procedure.
Here is my experience. Hope this helps others would be PRs.
Could not sleep last night thinking about AVR and what if I'd be denied re-entry to US and blah blah...
Reached Rainbow bridge at 9:30 AM on 05/31 along with my spouse and kid. Crossed it praying god that everything should go fine.
No traffic..As soon as I reached Canada side I was stopped at some toll gate kind of structure.
Officer at the window greeted and asked if I'm Canada Citizen. I said no and he asked for my passport and reason for entering Canada. I said landing for PR.
He asked some formal questions like did you buy anything at duty free shop, are you carrying pets in ur vehicle, any firearms, etc?
After I answered all his queries, he gave me yellow slip and asked to park my vehicle at immigration office.
As soon as I parked my vehicle, CBSP officer came out and guided me towards entry door.
I reached immigration desk and the lady officer asked for my passport, yellow slip and CPR.
Then she asked for proof of fund. I showed USD 8000 cash and USD 20,000 cashiers check. She asked for my address in Canada. I gave her Alberta address. Then she asked me to have a seat till she completes the paperwork. It took her around 30 mins and then she called me and asked me and spouse to sign CPR and said "Welcome to Canada. Now you are Canadian PR and you would recieve your PR card in 30 days. You should get your SIN and health card done now."
I went to Service Canada office (very near to rainbow bridge - 5853 Peer Street) and got our SIN application done. It took around 15 mins.
Spent some time at niagara falls to have canadian view of the fall.
Returning to USA ???
Reached Rainbow bridge at around 4:00 PM. There was a huge traffic in each lane at immigration gate (something similar to toll gate).
Finally my turn came and officer asked me for passport. I gave him passport and I797 for all of us. He then asked where do I live. I told him my state in USA. He said "your passport has expired visa. Do you know this?" I said yes. He said "please plan to get that done soon."
and he gave my passport and I797 back and let us enter US ;D
Thank you all for your help.