are not exactly one property per kid and are not all of equal value.

I still agree that value all of them by one method or the other consistently, but, then you need to figure out how to equalize values by having some with more valuable properties pay extra money into the pot

You could value the pot netting selling costs, give a pot of family bucks to spend to each sibling, in equal amounts, and then let siblings bid on each property using their family bucks or paying in real bucks. And that nobody wants - sell to the public.

Someone else explained things better than I did, but sell it all either to each other or the public or you will gave hard feelings forever.