Unfortunately this does not work. A MultiPoint object is an array of MapPoints, so when I click on a point on the map, event.currentTarget returns a MultiPoint, which cannot be coerced as a MapPoint. I need a way to distinguish which MapPoint within the MultiPoint was clicked, and as var as I can tell, neither event.target nor event.currentTarget will return this information.
It seems like this should be basic functionality, but I guess a MultiPoint is intended to be one cohesive graphic. The only solution I can think of is to not use a MultiPoint, but rather loop over my lat/long data and manually add individual MapPoints to the map so that they can each be clicked.