I think I'd go for the official site as it is closer to things 'at the top' but saying that, it isn't THAT close apart from things happening at the school. Whitby is a brilliant festival but I don't think it is one of the more accessible! (Although maybe there is provision for people with limited mobility?) Perhaps your friend could put up a notice in the festival cafe asking for lifts.
Sorry, that's probably not a lot of help! Good luck though.