What a wonderful idea for your school! I'll have to suggest it for mine.

It's always good to over-state the obvious when making suggestions on a poster:
play the local classical music station at mealtime. (If such a one exists! If not:)
Get classical/folk/jazz cds from your local library and play them at mealtime. Discuss the music, instruments, etc. during the meal.

Get gramma, grandpa to remember the songs they sang as kids. What a wealth of singalongs they can inspire!

(We have big all-school assemblies each week at our school. I periodically send home the lyrics to favorite assembly songs in a newsletter)
Have the children teach a song from school to the whole family.

Enjoy!
Allison