There are survey based methods to accomplish the same thing as a Vickrey auction does — get a full demand curve. In a lot of markets, survey methods are typically expensive and tedious to do because you have to find your customers and convince them to take a survey.
However, I think such survey methods would work well here because everybody takes one or multiple surveys in products they’re interested in as is!
In the case of already having some product to move, a Vickrey auction is a good tool to use, and the auction is already a second-price auction. If the prices got really high, I’d be inclined to donate some of the proceeds to charity (you can’t really have a price cap or something as that runs into fairness issues).
Running a Vickrey auction for your first group buy is crazy though. Do some market research.