I do not play piano, but classical/acoustic guitar.
Are your courses designed strictly for pianists? If your courses are open to all instrumentalists, are students required to submit their class/home work assignments scored only for piano, or can another instrument or instruments be substituted?
You do not need to be able to play piano to take the courses.
Most of the examples in the courses are for piano, as that is the best way to get theoretical concepts across. But you can compose for any instrument.
I recommend attempting to compose for piano, because then you can have complete harmonies, with bass lines, and a melody. But if you want to compose for single line instruments, such as trumpet, or other chordal instruments, such as guitar, that is fine.