You put this thread in the right place.
Natures, Abilities, and items are important too, so include those as well.
They all seem to be correctly EV trained to me. Thing is, you have Umbreon and Sylveon doing the exact same thing (you have both of them doing a Wish+Protect stall), and there's no point in that. Umbreon can't do much else, so its best to change Sylveon's set:
-Sylveon w/Leftovers
Nature: Modest
Ability: Pixilate is preferred, but if you can't get that, its ok
EVs: 252 HP, 252 Sp.Attack, 4 Defense
Moves: Calm Mind, Moon Blast/Hyper Voice (HV only with Pixilate), Shadow Ball, Hidden Power Fire/Psyshock
Also, swap Umbreon's Confuse Ray with Foul Play (or at least some sort of attack), otherwise it is absolute Taunt bait and set-up bait. Confusion is a bit of an unreliable status effect anyway.
Mawile and Charizard shine in their mega forms, not their regular forms. So they need their Mega Stones. I'm assuming your Charizard will be a Mega Charizard Y. If that's the case, replace Hidden Power with Solar Beam. Since Mega Zard Y has Drought, the sun will be up when its in play (so no charge turn for Solar Beam), and Solar Beam is the superior option since it has double the power of Hidden Power. If you keep Roost on it, you'll need to swap Air Slash with either Dragon Pulse or Focus Blast. Otherwise a lotta stuff will wall it. If its a Mega Charizard X, then a totally different set is needed.
I was assuming that Mawile was using Mawilite when I posted, but since a player can only use one Mega Evolution per battle, that was why I suggested Goodra in Charizard's place.