My experience is that a "friend" like this allways brings bad karma along maybe just due to your own displeasure or it really is bad juju. I had one of these friends come to Housotn and go sailing with me and had blown a head gasket in my engine and my head and about a half dozen other things go wrong. Another friend invited himself a couple months later and all the sudden had carb and fuel pump issues. Oh yeah the engine was only two months old. Then they both thought they could fix the issues better than I could and had to just let them tinker for a couple hours before I could make them believe that my diagnosis was correct. Aughhhhh.
I would just drop the ball on him and say enjoy your flight and get a hotel/resort. I know thats easier said than done but I can already tell from you post that you are stressing over this and just think to yourself about how you are going to feel when the time comes. This is your dream and will be your reality. Just my opinion and you know what they say about opinions.