You are fine. I'm sorry for your loss.
Are there any hobby shops near you? Most take consignments, which means you could probably move the planes pretty quickly if you price them right.
As for someone to buy them all in a lot, there are people who will do it, but they'll want to be able to make money at it. If your brother truly spent 100k on everything he had, the used value will probably be 1/2 to 1/3 of that depending on condition. An individual would probably get interested at 1/2 of that, somewhere in the 20k range. Even with that much discount, it might take some time to find a buyer.