U.S. forward Boyd made his Bundesliga debut after leaving RB Leipzig for Darmstadt in January.
McKennie was brought on for the final 13 minutes as a 10-man Schalke held on for a point.
Aubameyang, 27, the Bundesliga's top scorer, has been linked with Paris Saint-Germain and Chinese Super League club Tianjin Quanijan in recent weeks.
Pitchside reporter Britta Hofmann didn't escape without a soaking as Bayern Munich celebrated their latest title win with giant glasses of beer.
Performance on Saturday was part of choreographed celebrations of Bayern's fifth successive Bundesliga title.
Vidal, a Chile international teammate of Sanchez, has won the Bundesliga twice in consecutive seasons at Bayern.