As you want an LCD as well, How about one of the Serial/I2C controllers with combined support for the keypad.
Then its just 2 pins plus supply and ground.
Includes all the backlighting and contrast adjustment.
http://cgi.ebay.co.uk/I2C-Keypad-controller-LCD-Character-Display-/310275043982?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item483dd5728e
Libraries available as well.
Ive had a play and it works well.
Gordon