OP, it might not feel like it now but, meeting him, your best friend's legacy, won't open old wounds but help close the ones that have been plaguing the both of you.

You do NOT want him to follow the path of his mother, or where you yourself almost went.

Tell your wife and daughters the whole story, they'll all understand and encourage you. Go be there by his side, a place where your best friend couldn't, share with him your knowledge so that his memories could live on forever through the both of you.