To change where your FMV is displayed, Go to Software Settings > Auction Settings > FMV Settings.

For 501c3 non-profit organizations in the US, the IRS has some guidance for organizations regarding Fair Market Value and reporting. First, they say that in order for a bidder to claim a tax deduction on an auction purchase, they need to have known when they placed their bid that they were being charitable, i.e. that their bid exceeded the FMV.  This means that the FMV needs to be displayed somewhere in the system for the bidder to be able to see it. This is explained on this page: 

NOTE: If you use 'Priceless' as a FMV, the value that will appear on bidder statements is $0.00. This is because typically 'Priceless' items mean you cannot put a value amount on an item, also meaning no value, or 0.   Priceless FMV does not have any tax write off ability.  

Also, when it comes to receipts from purchases at the event, if you consider an auction purchase to be a donation in which the bidder receives some good or service in return, then the receipt should have the FMV of the good/service.  The quote is:

Description and good faith estimate of the value of goods or services, if any, that organization provided in return for the contribution;

and that is from this page:

** A great place to put your Tax ID number could be the Statement footer section under Software Settings > Auction Settings > Custom Content. This will show up on the bottom of all of your bidder's receipts.