Advice Needed - First time Vendor

We're selling our current place (2bd, 1 bath villa) in Sydney and wanted to get some thoughts. Contract is currently for an auction and we have already received a few offers (incl. one offer - 1.02mil - which we would be willing to accept).

REA have suggested that there are a few more buyers interested and suggested the possibility of an auction.

If we take our property to auction, would there be a chance that it sells for under the existing offer? What would you suggest?