You simply put the actions for each object within the family in the actions.
If there is an action for a specific object, but it is not picked, then the action doesn't do anything.
So pick top instance of family as a condition.
ObjectA - Do something
ObjectB - Do something
ObjectC - Do something
Only the instance that was picked would be affected.
Alternatively you can add an instance variable to the family/object as a condition to compare against to take actions.