I think you’ve laid out your options well. I will note that posting pictures of different individuals of a species in one observation is ok (I wouldn’t say it is incorrect per se), it can just cause some issues - one of which you’ve identified here.
There’s an existing and open discussion around annotations and potential issues here: https://forum.inaturalist.org/t/lets-talk-annotations/627
I believe that this issue (and/or similar) have been discussed to some extent (it’s a long thread…)