A thousand spastic birds in the pen would probably discourage them. If not, Reeves has a pheasant he can rent to you. I guarantee, that would work. I think I would kill off the offenders, though. Once any animal establishes a habit concerning food or shelter, it's hard to break. {Consider Welfare Programs}
That over revved kid did you a favor, though, huh?
I have squirrels all around. Have them raiding my strawberries all the time, not to mention garden vegetables. Garden is no more than 75 feet from flight pen. I've never had a problem with them. You might try a smallbox shelter over the feeders, so they don't notice it. Again, the ones that already know where it is won't forget, and will chatter to others to suck them in. {Another correlation with humans?}
Whatever you do, don't put out any D-con. It is toxic to squirrels.