Let me rate this too. I think I can give some different suggestions.
However, I'm not about to delve into LC EVs, so just bear with me.
Treeko: He's like a fast tank. It's cool. Even though you have quick attack on him, I think it would be OK to give him a Modest/Timid nature, because quick attack isn't going to do tons of damage anyway, it's just meant for finishing off the opponent. He's good, his set is good too.
Totodile: There's the good ol' Feraligatr set. He takes after his daddy. Looks good, good set, I assume Crunch is the neutral damage for other water types. If you wanted, you could give him superpower instead, because it's awesome. I'd give him eviolite to make him bulky. Don't listen to Unrecognizable, it's fine ;)
Chimchar: OK, Let me provide you with a different set.
Chimchar @ Flying Gem
EVs: As many as you can in speed and attack
Nature: Hasty (+Spe, -Def)
Alright, this is the awesome mixed attacker. He'll hit hard with overheat when he needs to, and gets coverage on water types with thunderpunch. Acrobatics is more powerful than a STAB fire-punch, and still kills the grass things. It should work well.
Squirtle: He's probably going to be your defensive go-to dude. He'll be your toxic staller. I see you threw in HP fire for the grass types, but you can go ahead and give him Ice beam, for more power. Give him as much HP and SpD as possible, with a Calm Nature. This will allow him to take more Giga Drains and Energy balls from the grass types. Give him Protect instead of Rapid Spin, I don't think entry hazards are going to be a huge threat.
Chikorita: Alrighty, since you already have a toxic staller, let me give you this different idea:
Chikorita @ Eviolite
EVs: As many as you can in Physical Defense and HP.
Nature: Bold (+Def, -Atk)
This guy will be your dual screener. He'll allow your Squirtle to live more attacks, making him a more effective toxic staller. Chikorita here will also heal you up with aromatherapy. He should work pretty well.
Charmander: Keep the set, but replace Brick Break with Dragon Claw. He looks like a good sweeper to me, but life orb with flare blitz could make recoil hurt, so give him Eviolite instead, which will help him get up more dragon dances.
Alright, please give me some feedback. Good luck to you and your LC starter team, and good luck in the tournament.