Burnside, I don't think it's a good idea to give discount for shareholders because lots of them may not involved in purchasing the code. But I think you can distribute the sold money to all shareholders proportionally. This is more fair and reasonable.
It should work out the same either way, one way the buyer pays a larger amount but gets some of it back, the other way the buyer pays less but does not get any of the distribution, which goes to the other shareholders.
Yup, with the primary difference being the dilution of my own shares. In effect, I would grant a current shareholder some portion of my shares prior to final distribution if they in fact win the bid.