There are several other instruments which are related to the piano which are important for us to introduce to school students. They are the organ, celesta and harpsichord.
Show and talk about the different aspects and characteristics of the keyboard instruments. The keyboard instruments are related to each other in that they are controlled by a similarly laid-out key mechanism. However if we are to be technical about it each of these instruments really belongs in a different family.
The harpsichord and the piano are string instruments (chordophones). The hammers on the piano strike the strings, while the harpsichord mechanism plucks the string.
The pipe organ really belongs in the wind family. Wind is blowed through the pipes, sometimes like a whistle, and sometimes through a reed like a woodwind instrument.
The celesta is a compound idiophone like the glockenspiel, only it uses a keyboard mechanism rather than mallets.
Perhaps you might also discuss these things: There is only one row of keys on a piano or celesta, however on the organ (and most harpsichords) there are nearly always more than one keyboard. You might also notice the various ranges of the instruments – Organs and Pianos have an extremely wide range, while the range on the harpsichord and celesta are much more limited.
This is a tiny sample of the music lesson plans available from the fun music company.