what are their ages? that may clear up some things before i respond since young kids are way different then older ones.

The girl is 12, and the boys are twins, at the age of 9. They're even doing it as i type this. please help me

Try painting their feet with a 'stop n grow' liquid that is used to stop children from biting their nails, it will not harm them but will taste horrid. You can buy this stuff from most pharmacy's(use daily). Don't worry about them running barefoot round the house it is good for them. But obviously from a germ point of view the foot sucking should be deterred! Good luck and happy Christmas.

you too :) i hope this works.