I agree with danko.
I think you'd be well advised to go to a stamp club meeting and lay it all out on a table by country. Invite offers.
If I was going to opt for selling on line, I'd post one of two pages of the very oldest / most rare if you know which are such - and say in text that "total collections amounts to......whatever volume / number / cat. value. And spans which years. Include statement of general condition. Of course M/U or both. Having said all that I have had very little luck selling world in either
ebay.com or
ebay.uk. Just as one example, I have a large older / very good condition used Cuba collection that I've been trying to sell on line for several years. Never a bid. of course that reactionary
ebay.com bans Cuba selling (how dare they!!) but there are ways around that.