This is probably something I should think more about. :/ I have a pretty darned big collection of collections--MLP, Breyer, dragons, other horse-shaped objects, Disney pins, and miscellaneous stuff. (Books and comics, though pretty much all of those could go to a library/used bookstore.
I have no children, but I have 2 nieces. Though they aren't as horse-crazy as I am, they both have expressed liking for certain items, and those I'll have to mark down for them. Example: the younger niece has always loved mermaids, and the year I took them to Breyerfest there was was a special run horse made of clear, blue-tinted plastic and had a mermaid design all over it. She called dibs before I even bought it.
I guess it will depend on who goes first--me or my husband. If it's me, he has instructions on who to trust with selling off the ones my nieces don't want. If it's him, I'd better pick a new "collection custodian."