I agree with Carol.
If there was no rule we'd be flooded with photos of no family history significance and where no permission had been given by people in the photo. But we've all restored old photos on here where the situation is similar to yours.
As Carol says, give it a go.
If Sarah's not happy with any particular photo, you could pm one or more of the restorers asking them to have a go at it and exchange the photo by email. Of course the preferred method is to do it on the board so all restorers can have a go and the results can be displayed for all members to see.
Cheers,
Peter