hi ..I think your system needs only keypad and lcd.
you can use 4×4 matrix keypad. and i think 16×2 LCD is enough for mentioned operations.
You can get ckt for interfacing of 89c51 with lcd and keypad here itself in EG in LABS tab.
Coding of interfacing is also available here itself. Follow the link below
Your main aim should be your logic for your application and that will be very interesting.