You might get some information from my homepage at http://members.home.nl/bzijlstra
If I had this 'problem' I would take two PCF8574 I2c-IC's, put on the first one a 4 x 4 keymatrix, on the second one a LCD in 4-bit mode. All this can be found on my homepage (in assembler and in BASCOM-8051). You can take any 8051-derivate to connect the keymatrix and LCD to, I2c can be made by software (like I did) and by hardware. You can even consider to download a demo-version of Bascom from www.mcselec.com with which you can make up to 2 kb hexcode for free. Just to get the hang of it. Succes.