Crafts by amanda has a cute idea for napkin ring. Her tutorial is a bit involved and includes making the beads out of clay and painting them and using wire and a hot glue gun to secure the ends, but this could be easily adapted to a kid's craft with ready made beads and some cord with a pretty knot to tie the ends.
Good for ages 7 and up.
Get the instructions here:
http://craftsbyamanda.com/2012/04/pretty-spring-napkin-rings.html