Hi everyone from S.W. France et salut Joseph. I am a new member and a accordina player, this kind of melodica with a button accordion keyboard.
The accordion keyboard is not more complicated than the piano keyboard, it is different. Its layout is logical and regular : always the same notes at the same position in all octaves. When you figured out this keyboard, tunes you already know come quickly.
http://en.wikipedia.org/wiki/File:C-Griff.svg (accordina has only the three lower rows)
Some videos with different accordinas :