I would sell them all.
But thats because they arent my watches. I wouldnt sell my watches. Dont sell anything, if you dont HAVE to. You might regret it. Its just a handful of watches, put the ones you arent using at the bottom or your sock drawer or something. lol
Fuck that, keep them.
He didnt want his wife to know about them, nor to have them.
You should honor your word, and the wishes of your friend.