Yup, and when your kids draw on the walls amputate their fingers at the
first knuckle.

Alternatively, spend a few bucks on a scratching post, and rub some of your
worn clothes on it to make it smell "right".

Or, spend even fewer bucks on a large doormat (or a cut off of carpet,
turned upside down so the rough side is up) to place outside the doorway
they scratch at (or spend quite a few more dollars on a doormat tacked to a
bit of wood which pet shops would call a scratching board or similar).

Cat scratching is an essential part of their daily lives, they do it to
exercise their shoulders, keep their nails in good shape, and most
importantly they do it to scent mark their territory (my cat only ever
scratches at the front and back doors, I expect they may see your bedroom
doorway as the edge of their immediate home range and they want to leave a
scent message there to warn off other cats). Sometimes they will scratch if
they're frustrated (like they can't get in a door they really want to).

It is likely to be near impossible to completely discourage them from doing
it, but providing them with a place that is acceptable to scratch should
help, if not solve the problem entirely; please give this a try before
maiming your cats!

Steve