Galileo was the first scientist to use an instrument to study the sun (telescope). One feature he was able to observe were sunspots. I built a simple image projector for our campers to use to observe the sun the summer of the total solar eclipse. You could make one for your students to use to observe and track sunspots.
Here is the link: http://richardsont.people.cofc.edu/safe_solar_folder/index.html
I also agree that the Parker Solar Probe would be a great mission to observe with your students.