There is a crisp, cheerful, C-major Haydn piano sonata that would be a consummate choice for music. I think Haydn even wrote it for a wedding, is the story behind it. The notes of the theme are: C above middle C, then G, E, A, D, G, C. If I were a guest at your grandparents' golden wedding, I'd make a special point of doing that Haydn piece for them. I mean, it really says hello.