The piano has several less known cousins which are important for us to introduce into the music classroom: the celesta, harpsichord and organ.
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. Technically, however, they belong to different instrument families according to how they produce sound.
Both the piano and the harpsichord are really stringed instruments. 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: the piano and the celesta have a single manual (row of keys), whereas some harpsichords and virtually all organs have multiple manuals. Pianos and organs have a very wide range while harpsichords and celestas have a more limited range.
This is a tiny sample of the music lesson plans on orchestral musical instruments from the Fun Music Company.