How old are your parents? I know it shouldn't be a determining factor, but some of us might ....actually be that age ..and would be able to give a sense of what is cool/not cool these days.

Start with: What do your parents like to do together as a couple in terms of hobbies/interests? And with some of their friends? If you know their friends like dancing, then have some music with small dance space. Are your parents outgoing? (Mine aren't, they are introverted. )

This is if you run out of ideas aside from some retrospective on their marriage --how they met, their wedding day, etc.

That might help you add some stories or determine a theme for party dinner.