You'll never know if you never ask. As harsh as it may sound, you're gonna have to ask him to his face. From a personal perspective, regardless of whether I accepted the invitation or not, I would have great admiration and respect for the girl because she had the courage to ask me out.
Too many people miss great opportunities because they're afraid of what may happen when they're open. Don't be one of these people.
Just ask him out, be genuine about it, and see what happens.
Best of luck,
- Gutz