You are wise to include in your will how your guns are to be distributed, as well as leaving instructions how they are to be valued and suggestions as to how they can be marketed to get fair value. In my experience, not all heirs are interested in guns and would just as soon have the cash value. Similarly, not all of the guns are "special" and may readily be sold.
It may help if they are specifically referred to as "family heirlooms"...at least the prized guns! That could possibly give a basis for a lawsuit against someone who "disposes" of the guns in the future without notifying the rest of the family. (A real gun hater...such as my sister-in-law!...will simply drop them off a bridge into a deep lake rather than let anyone else have use of them.
)
I recently went to an estate sale including the accurized firearms, expensive reloading equipment, components, and shooting gear of one of America's past shooting champions...it was really, really sad. The family, none of whom were shooters, almost certainly did not get 10% of what the stuff was worth. That was a real "wake up call" for me...
Example: One of the items was a M1A SS barreled rifle with adjustable cheekpiece and a large, clunking heavy scope including a block attached...I couldn't readily identify the tactical scope as the external ID was all covered by the blocky mechanism. No one knew what it was, and no one bid on it. At the close, the family still had the rifle and wanted to dispose of it...asked me for an offer. To help them out, I initially offered $1,600 for the rifle alone...I had a nice Leopold scope at home to put on it. The family counteroffered the entire setup for $1,800...which I took as I figured I could sell the scope for at least that difference.
When I got home I noticed a "BORS" ID on the bottom of the block...researched it on INET, and was shocked to find that I had a Barrett BORS computerized sight paired with a Leopold Mk 4 scope! Also found that the rifle with its rather unusual stock had been accurized by the Army Marksmanship Unit. I had an easy $5,000 worth of rifle for my $1,800!