I'd suggest keeping both of the black "pencil curl" hats for his sons, especially since they're similar.
"Also, what should I consider when choosing the other hats to keep for the boys?"
That's a question that all of us struggle with every day, just for ourselves! :)
I think once you have...
Mrs JW, you have my sincerest condolences.
I suspect that might be this hat he posted about in the below thread:
"Wearing my favourite hat today. Stetson No 1 Quality - very thin lightweight felt. I recently discovered this one might be as early as the 1930’s"...