If you want to minimise cost, delve into your kitchen cupboards for tin foil, greaseproof paper, cardboard boxes (eg gravy cubes, cereal). cut up old clothes for a variety of fabrics & textures, buttons & wool.
save packing from parcels - bubble wrap, packing wotsits or chips etc. cut up old catalogues, magazines.
Provide scissors, pva glue & spreaders, pencils(coloured & 2b)/crayons, oil pastels/felt tips & a variety of paper.
Discount shops can be useful source for cheap wrapping paper, tissue paper, wallpaper roll, paper plates etc
You can get packs of feathers, googly eyes & funky foam etc from art shops or take a look at these for inspiration:
www.craftpacks.co.uk
www.bakerross.co.uk
www.smitcraft.co.uk
Recommend plenty of newspaper or plastic tablecloth.
hope the kids have fun!