Is it still cannon the Bennu had something to do with the Birth Of Magic, or is that completely over-written with the Old Gods choosing to kill Phanto?
I think they still had something to do with it, they were just not the direct cause of it.
So far, we have had no factual information that states that the Bennu started the Birth of Magic. All we know is that a ghostly Apparition told the explorers in the Unexpected Discovery campaign some facts about the Bennu people. We don't know if that Bennu Apparition is telling the truth or not. If the information has not come from Rawb himself, it should be tenuously considered canon, because we don't know if they are lying or trying to deceive us or not.
Bennu Obstacles = Theme Parks?
Where did the lore that Bennu Obstacle Courses were Training Courses for Elves, and that the Elves considered them "Theme Parks" come from?
I do believe that it was in the Unexpected Discovery campaign, around episode 6 or 7 on Youtube, with the Beenu Apparition.
Read the lore cards