Talk

Do you want them to take it home? What if you made a big green christmas tree out of green paper, stick it to the wall and get the children to do baubles to stick on? You could cut the bauble shapes out of paper for the little ones and get the older ones to do it themselves, maybe with a prize for the best? Get one group to do a fairy/star for the top? That way the thing will grow throughout the exhibition to a lovely finished artwork for the library.

That's a very good idea plantsitter, - I'll have to check out the wall space in the library, and whether we're allowed to stick stuff up (it's not my local library, so I haven't seen inside it yet), but I think the children would enjoy coming back every few days to see how the tree was progressing

If it is flinging glitter around you like these stained glass windows have gone down well with every group of kids I have ever done it with.
If you are doing it with groups, provide the glitter in tubs with plastic spoons (much less wastage) and precut lots of strips of wool to help. Younger ones will need help setting up the window.

For a group activity you could do a large collage, draw a scene on some wallpaper or similar and let the kids fill it in with fabric, tissue paper, coloured paper etc.

Or for individual crafts maybe tea light holders - old jam jars covered with glued on tissue paper. Or Christmas tree decorations made from pine cones covered in glue and rolled in glitter.