Let me say a few things-
-Dragon Dance is better than Swords Dance on Charizard.
-Future Sight is pretty bad and you should replace it with Psyshock to hit Chansey and other special walls.
-Mawile likes using Swords Dance more than Power Up Punch
-Gardevoir should use 252 Speed EVs over Special Defense
It really depends on the rest of your team, but I'd say that if you change what I suggested you change, Mega Mawile would be the best, but note that it's banned in most Smogon formats.