The idea came from this book:
Each child needed a balloon, a small box (e.g. a shoe box), some modelling clay, tape, PVA glue mixed with water (2:1 glue to water) and lots of coloured tissue paper.
First, we blew up a balloon so that it fitted snugly into its box so that it wouldn't move. We found that a little extra tape held it more securely.
Then we made features for the face out of modelling clay and taped them to the balloon.
Next we stuck on strips of tissue paper with the glue and water mixture. We used lots of glue so that it was really soggy when we had finished. Each child did 3-4 layers of tissue paper, and it turned out pretty well (though more layers would be more solid).
The masks were left to dry over night.
Next day, we burst the balloons, removed the clay, trimmed the edges and cut out eye holes.
Note- very messy! There was glue and tissue paper everywhere.
This was quite a good craft for all ages. My 3 and 6 year olds needed some help, but could do quite a bit on their own and got good results. My 7 and 9 year olds managed with very little help.