As far as I know, Barrie never had any interest in golf - cricket was his game and passion. It is of course quite possible he knew Robert Forgan, being a fellow Scot, but I've never seen it mentioned in any biography. I think it is more likely that the name 'Peter Pan" was used for marketing purposes, to make the most of the work's huge popularity at the time. Whether or not they asked Barrie's permission to do so is another matter...