Maybe I was naive, but I have seen stuff sell on the Stout Auction site for way more than I thought they were worth. And I have bought many items from Stout and resold them on ebay...so I do think a train auction house such as Stout would be a better venue than a regular auction house.
When my father passed, we used a local auction house for the furniture and other odds and ends no family members wanted and we were very pleased...even with the auction house fees. We also sold some of my dads G gauge stuff...nothing major a Bachman set and some other odds and ends...got nothing for them really. I kept a few freight cars and sold them on Ebay for much more than the uneducated auction house.
If he is selling more than just the trains at the Auction house, hold back the high ticket train items and sell them on ebay or Stout...but it is a hassle to list and ship and worry about breakage in route, etc, etc. Or tell him to list them today on Ebay...and if they don't have bids by Tuesday cancel the auction...nothing lost!
