I wouldn't give them to a pet shop to be honest. What about some kind of rat sanctuary that specialise. Somewhere you know they will go to good homes.

or advertise for good homes, then check out where they are going, remember you can also ways keep in touch with the new owners if you do it that way.

I was sorry to hear what has happened but why did they let you get so many in the first place??

Hope all goes well for you.