What a pragmatic way of dealing with your grief. Good on you.
The OM1 was an iconic camera, the smallest and lightest SLR ever built - so there is one good reason to keep that one. The OM10 was simply an auto version of the 1 and so as it was what you had to use with your Dad, then why not keep both the 1 and the 10? It isn't going to break the bank. There was the OM2 running at the same time and the 10 was a more amateur version of more or less the same auto/manual camera.
The PenF was another iconic camera in its day - which is why they have just relaunched the name, trading of the nostalgia of the previous success.
The Leica M2 would be my choice from those. But it depends on what you are keeping them for. You try replacing them now - they will fetch really good money.
One piece of advice that nobody has suggested is that you get in touch with one of the specialist auctioneers, say Christies, or Bonhams. Tell them what you have and ask them if they have any specialist collectors sales coming up - you are likely to get a better price at these sales than on ebay. Either that, or get in touch with specialist collectors groups - it can't be that hard in this day and age. I would certainly not rush into selling anything just yet, other than the more "ordinary" items, such as the Zenits.
Make an inventory of everything - maker by maker. So have a list of all the Leica stuff, both SLR and Rangefinder together, one at the top and then the other at the bottom to seperate them but have them together. That way you will be abble to make more of an informed decision without overlooking anything. Take your time and look for some advice from a specialist and from collectors groups. I think you will be surprised at how rare some of that is, especially if it is boxed and in good condition.