Problem Solving vs Tattling

So at what point is "coming to tell mom" tattling or problem solving?
My oldest child is just getting to the point where problem solving is more than a physical response and he is beginning to understand not to hit or cry/whine when something does not go his way and when I am trying to teach him to tell me so that I can change the activity or steer him to another toy/distraction.
But I was thinking about this parenting thing as I was working on someone else's house with another lady who had 2 of her kids (a 3 1/2 year old boy and a 5 year old girl). 
I decided it is hard to know and establish to a child the difference between tattling on someone or learning how to get a mediator involved in the situation.
The personality of my child comes out when there are kids who whine or cry more then others.  He tends to egg those individuals on.  I can't decide if it is a conscious thing and he likes to hear others scream/whine/cry or what he is trying to do, especially after I repeatedly tell him to "back off," "to "leave them alone" to "find a different toy"... etc.
Yesterday was going pretty well until the other little boy decided he no longer wanted to play with my boy unless he initiated it.  So every time my son got too close to the other boy there was some whining heard.  So I tried to be the mediator after it got too annoying (to me) and give my child something else to do (i.e. help me with my task).  The little girl was actually playing well with my son and asked if she could help as well.  Peace established...for 2 minutes until the other little boy wants to do what the others are but mostly wanting what my son has and then ensued a big fight/tantrum (that got my child timeout for not sharing and taking turns, and me wishing the other mother would help with this problem because I can't put her son in timeout for hitting or not sharing back and I don't want to go "tattle.") 
Finally the other mother asked why my son was upset and I tried to explain why he was crying and in timeout and so she did get involved.  After things settled down I tried to be ahead of another issue by putting my son on another task...outside, which as soon as I did the little girl was willing to go help him and then they got to playing.  Peace established again!  Eventually the other boy did go outside to join the others and either I couldn't hear whining or my son stopped irritating the other little boy.

This was a rambling story but my whole issue of the day is when I'm telling my child to just come tell me so that I can help with the situation and in my head I am wondering, "I am teaching him to tattle?"  Or when I am trying to mediate with my child but the child who has the problem puts himself right back into the picture.  I feel bad putting my child in timeout when the problem he was causing is solved and now the problem is not really being caused by him.  I know the principles of sharing and taking turns apply to all situations which is why timeout was issued but I feel bad punishing my child when he was trying to just do the task I gave him.  (I sometimes feel I am the meanest mother)
Oh the joys of being a parent, not only are we trying to teach right from wrong but we are also getting a crash course ourselves...or at least a different perspective of the rights and wrongs!