Go with 4 emoticons, each assigned to a button, 4 buttons.
Or I believe you can set your program to react according to how long the button presses were held in for.
So one button with a quick press, press and hold for 2 secs, 3 secs, etc.
Whether the width of the display is horizontal or turned vertical; I don't think that is going to pose any problems with your emoticon other than size.