In answer to (some of) your questions:
Roger Lancelyn Green in his book 50 Years of Peter Pan writes that Barrie was “greatly disappointed” and quotes the latter’s reaction after seeing the film for the first time: “It is only repeating what is done on the stage, and the only reason for a film should be that it does the things the stage can’t do.” It had already been a disappointment that his own scenario, with his very far-seeing vision of special effects wasn’t used. He did approve of Betty Bronson though, as he had selected her himself.
One would suspect he didn’t think much of the American flavour, as he was a proud British man, as well as a proud Scot., and the play has so many references to its Englishness, from Eaton to King George.
Great Ormond St Hospital did not benefit from the film since it was made 5 years before Barrie gifted his copyright to the hospital and there were no royalties payable, before or after.
I have no idea about Alan Hale being one of the pirates, and like you, couldn’t find any mention.
I loved your dad’s anecdote, very funny.