Kids'll see right through any lack of interest or belief you have in the music. I would simply look at the task as a performance - and play whatever songs are your favorites, at the moment. Talk about your long and varied career in music, play examples of songs you played in days gone by - but keep the whole thing in context of what you LOVE to play/sing right now.

The joy of your music is what opens the door to their appreciation - any wisdom you impart from your introductions, stories or the lyrics is gravy! It's Rick Fielding that is the primary lesson, and I'll bet that's the easiset to display.