I think you should go ahead with lower minimum amounts. I do not think that it is unfair for the current bidders as everybody still has the chance to buy some of the remaining teams for a low amount. Also, it would increase the pot available to the winners no matter how much you get from these bids. However, it does not necessarily have to be the case that this will increase the profit for charity. If one of the teams with no owner should win any of the prices, their full profit should go to charity.