I think the Facebook page could be for more fun and light topics and chat, with crossover posts from the main website, and other sites whenever there’s something particularly interesting. The uncomplicated format lends itself to quick, conversational, ‘throwaway’ posts. There will be some people who will not join a forum, but would readily post on FB. You can see that there’s already been several posts in the few hours that its been open.
I think this forum website is a searchable mine of information for the serious player, and I like that it is independent of FB, as Facebook can (and does) change the rules at any point – it probably isn’t the safest receptacle for all of this precious info.
So my suggestion is FB for melodica chat, and the forum for serious issues!