Many instrumental teachers teach just one instrument; however, I find it more fun for myself to mix it up whenever possible and teach at least a few different ones. Currently, I teach piano, keyboard, ukulele and a few wind instruments. I have also taught percussion and tuned percussion; I’m hoping to go back to teaching the xylophone very soon.
Of course the level up to which you can teach each instruments varies. For me, naturally the piano and keyboard are taught to a higher level than the other instruments as they are my main ones that I learnt before any others. Personally, I found it interesting to learn the other instruments and the learning process really helped me with developing my teaching style and understanding different learning styles.
Being both a teacher and a student is rewarding and the best way to finesse your teaching methods!