Get them to make papier mache bowls.
1 bowl covered with cling film/plastic food wrap
Lots of torn up tissue paper
PVA glue watered down 50/50
Cover bowl with lots of layers of tissue paper, and leave to dry. You can speed things up by cooking it in the microwave, but check it every minute or so, otherwise it will scorch/catch fire ( I speak from experience).
When dry, paint with acrylic paints if desired. Or leave it white - it will have a lovely translucency.
Apply another layer of glue mix to the inside of your bowl, and decorate with pressed flowers. I've also scattered the dusty bits from the bottom of my bag of dried rosebuds, to give it a 'summer meadow' look.
Alternatively, use coloured tissue paper and decorate with sequins/glitter/pretty threads/stickers or beads.
Leave to dry, and then apply another couple of coats of glue inside and out.
Have a great weekend.