Ensemble playing can be especially fun with the harpsichord. Many public school programs teach the recorder, and the harpsichord is the ideal instrument to accompany it. Also, much of the beginning repertoire for strings is Baroque. Many times one of your piano students also plays the violin in the school orchestra. If student lessons overlap or if you hold group classes, try some Baroque duos.
Baroque accompaniments are some of the simplest that exist.
A simple figured bass realization that sounds painfully naked on a piano may seem more complete on a harpsichord. The Baroque selections from James Lyke's Ensemble Music for Group Piano and the elegant but not too difficult sonatas for two keyboards of Padre Soler are just two possibilities. The harpsichord can be good for your students, but it can also be good for you. Because it is easily portable, performances are possible in churches or schools where adequate pianos are missing. I have toured throughout the Spanish countryside with my harpsichord snugly tucked into the back of the car, and played in places not on any map.