We used "We Thank Our Lucky Stars" year before last...lots of stuff out there. Star baskets, star candleholders, globe paperweight with stars, almost anything is out there with this theme...good going. Video (When You Wish Upon A Star...neat and easy.)

How about "Thank Heaven for Volunteers"? or "There's a Special Place in Heaven for Volunteers",or "Volunteers are Shining Stars"?

Volunteers are superstars, Volunteers are shooting stars, Volunteers light up the night sky, Wish upon a shooting/falling star~volunteers make your dreams come true.

Here's another idea for the star them.

Though we could search both near and far, you always be our brightest star!

We thank you so much for all that you are, you are invaluable to us, you're a shining star!

Hope this helps!

Juli