Need advise ASAP on family-based petition

[Zhykd4]

Me and my wife will be taking our oath taking for citizenship this coming July 27. My wife will be petitioning her parents after we get our certificate using I-130. Her mom and dad will be filing I-485 to change status simultaneously/concurrently with my wife. However, their I-94 will expire about 4 days (July 31). Should we file for extension of stay I-539 OR should they just proceed with I-485 (change of status) hoping they would let them stay indefinitely while it is still in process? Will her parents be considered unauthorized to stay after the I-94 expires, even when the forms were already submitted prior to the expiry date?

[newacct]

They should definitely NOT apply for B2 extension of stay. That would require them to attach a statement which explains what plans they have made to leave, which would be a lie since they plan to stay.

They can file I-485 either before or after their status expires. It doesn't make a difference to their I-485 either way. They can stay while their I-485 is pending.