I think my position is similar to that of a lot of the posters in this thread. I have accumulated a lot of firearms; some were given to me by or inherited from my father (he passed 6 years ago). A couple of those were guns I would never use so I sold them and got something that I wanted and now use regularly. My dad was a "wheeler-dealer," frequently buying/selling/trading guns and I think he'd approve of me following in his footsteps. He was a huge Browning guy, bought many new Belgian-made firearms in the 1960's. I still have a few of those and use them occasionally. I am now 63 y/o and have no sons but two daughters, one who is married. Her husband I haven't been able to turn into a hunter (though I've tried!). I'm hoping and praying that couple gives us a grandson or two; if they do, I'll likely pass on some firearms to those boys. If they don't or if I don't have interested heirs via the other daughter, I'll likely pass on a few guns to nephews who hunt with us. Other firearms will likely be sold when I'm too old to use them and/or I'll leave instructions for my wife regarding what to do with them if I pre-decease her.
The thing about the sentimental value angle is that I don't believe a gun will mean all that much to an inheritor that isn't my offspring or grandchild. While nephews like us uncles, there isn't that real, fond connection, at least in my case, so I'd say don't get all wrapped up in thinking they will value it all that highly and if you want to sell some, go for it.
All that said, I'll share a cool story. When I was a teenager, I received from my maternal grandfather an old, Stevens single shot .22 bolt action, probably in 1974 or so. It was not much of a gun but the only one my grandfather had and I was his only grandson. I had it for a few years and shot it occasionally. Then in the mid-70's Remington brought out their Model 66 nylon .22 semi-autos and I just had to have one. I didn't have a lot of cash back then so I sold my Stevens .22 to a neighborhood buddy, with the okay given by each of our dads, and put that cash towards the 66. I love the 66 and still have it, it's pristeen and I think pretty valuable (mine is the Apache Black/chrome version). So a few years later my grandpa passed away, in 1979. Flash forward another 20 years or so and I really started to regret having sold the Stevens .22; as an adult I realized the sentimentality of it. But here's where the story gets good. About 10 years go by and my wife and I are at my younger daughter's pee wee soccer game. During the game I recognize on the other sideline, a guy whom I think is the guy who I sold the Stevens to some 30 years ago. He's a parent of a kid on the other team. I hadn't seen him in probably 20 years or so. So after the game I go up to him and re-introduce myself and we have a nice chat. I ask him if he still has the Stevens and he said yes; I mentioned that I wish I hadn't sold it. The chat ends and on the way home from the game I tell my wife all about this then kind of forget about it. Then a few months later on Christmas morning, my wife says she has a surprise gift for me. Lo and behold, she comes out with....yep, you guessed it, the Stevens .22! She had secretly reached out to the guy and bought the rifle back for me. Maybe the best Christmas gift I'd ever received, at least as an adult. So now, I will definitely pass that rifle on to either my grandson if I have one or to one of my nephews if I don't, and encourage them to keep it in the family forever.
Sorry for rambling on so long, just wanted to pass that story on. Merry Christmas!