I use my bell if I'm riding on an MUP and I've stupidly come out when there are families with toddlers meandering around on the trail.

I slow to the safest speed required while dinging until all the toddlers on riding toys see me.

Even though I'm not going fast enough to scare anybody at that point, it's nice to have everybody of all ages make eye contact with me as I'm passing, to lessen the chance of them (especially the toddlers) from going right in front of me at the worst possible time.