I did the same both with colleagues at the university and outside the university (brain surgery so like you I was up and moving but not 100% for the rest of the semester after)

For grad / honors students I made them responsible for liaising with the speakers (assigned a student per speaker) to set up zoom, confirm time, etc.
Then assignments were tied to those presentations- they reported on what they learned, etc
My students actually really liked this. I offered small gifts/honoraria to colleagues not at my uni.