It has outstanding weaknesses to Rock and Ground, so you may want a pure Grass-type in there, or Fighting, or to replace Butterfree with Pinsir at some point (though the last of these would still leave a notable Rock weakness, which will only increase when/if Charmeleon evolves). I'd worry more about the weakness to Rock, since Earthquake users won't show up for a long time yet. Clefairy and Jigglypuff are also worth mentioning, one or the other. I can't say anything about movesets for third generation; hopefully someone else can.
Apart from that it seems quite balanced. There's honestly not a lot of room for comment given the team's low level.