I agree, lead by example...

Indah says "Scuse me" to everything as well, bit's of furniture as she squeezes past etc..
She always says Sank-you Mummy, Daddy, maddy, Poppy (yep even to the dog if she brings the ball to Indah!)
She always says please as well & if Maddy doesnt say Thank-you or Please Indah reminds her!

If you always yuse it the kids will use it too...