If that's your "Plan B" (well, Plan
s B) then it seems to me that if you <sigh> DO go ahead and get more chickens, it should be up to your aunt and Marlinchaser what to get and what age and so forth, since they are likely to end up with the product
IMO, if you are considering an auction as a means of handily disposing of extra chickens, you might want to reflect on where the chickens go from there and what kind of lives they lead from then on (and how soon cut short by disease). If this is a hobby flock for you, then it might be nice to prioritize the chickens' welfare, which is probably NOT best served by sending them thru an auction, exposed to bazillions of Happy Fun Germs, and then getting hauled off to live in what has a pretty fair likelihood of being conditions that you would not consider acceptible to keep them in *yourself*.
I'm not saying auctions don't have a place in the world, I'm just questioning whether they are really a good
a priori plan from a chickens-best-interest standpoint.
So, if you HAVE to get more chickens, see what kind(s) and ages and numbers your aunt wants, or Marlinchaser, and get that
Good luck and have fun,
Pat