My husband's piano teacher always used to perform at his recitals. He says the parents and students loved it and looked forward to it each year. Why not try it and see how it goes unless you have a lot of students and your recital is already longer than 40 min. I would pick a piece that is not too long and is an old standard in piano literature. That way, you could talk a little about it at the lesson and the students will learn a little music history!