Adeline, Resplendent Cathar | A Guide To Every Deck In EDH 

So I wasn't sure myself, so I looked it up and you are right Melee means “Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked with a creature this combat.” And according to the CR 508.6. A player is “attacking [a player]” if the first player controls a creature that is attacking the second player. A player has “attacked [a player]” if the first player declared one or more creatures as attackers attacking the second player. So you only "attacked" as many players as you sent creatures at during the declare attackers part and the tokens won't get the buff themselves since melee triggers on (declare) attack