Your vet sold you a three week old kitten? I'm sorry, but that sounds like an incredibly irresponsible thing to do unless something happened to the kitten's mother.

You should be able to get plenty of good advice both here and on other web sited devoted to cats.

Also, (sorry if I'm sounding really harsh here) - but a pet is a huge responsiblilty. They aren't toys and shouldn't be purchased to please a child's whim.

Finally (gosh, I'm on a soap-box now) - if this small kitten is too much to handle, perhaps you could return the little thing, and take your children to an animal shelter where they can adopt an older cat that will be much easier to cope with.

Good luck, sorry if I came across too grouchy, but both your well-being, as well as the kitten's is at stake here.

good luck.