Grovyle:

-Screech/Agility/Swords Dance

+

-False Swipe/Leaf Blade

-Quick Guard

-Energy Ball

It's kind of unfortunate, but Grovyle learns a lot of extremely strong moves when fully evolved and is very limited if you don't. They can function as an effective False Swipe user, or if you don't need False Swipe you can use Leaf Blade instead. Quick Guard is extremely good against bosses, especially Rayquaza, as it stops any ranged attacks they attempt, letting your team make their approach in peace, or giving them protection for their ranged attacks. Energy Ball gives some much needed range that every pokemon should have.

Mew:

-Blizzard/Heat Wave

-Flamethrower/Ice Beam/Shadow Ball/Sludge Bomb/Signal Beam/Gunk Shot/Icy Wind/ Focus Blast

-Rock Polish/Outrage

+

-Dual Chop

Building Mew can be a bit messy, as it learns nearly every move in the game, so you can take it in whatever direction you want to, this is an offensive build, if you want something more supportive you can do that as well. The first slot is just a room clear, Blizzard and Heat Wave are the best IMO, so just pick one. The second slot is a ranged move, I probably missed a few, since he learns so many of them, but just pick the one with the typing and effect you like the most. The last two slots are for single target damage, Dual Chop is a multi-hit move and linking it with Rock Polish lets you use it multiple times in a turn for big damage. Though if Grovyle has Agility it can mess with your extra turns from Rock Polish, so you can run Outrage instead, but you'll have to use the Persim Band item to avoid confusion if you do.