Lets take a look at your Pokemon first. Most of the levels are good. Perhaps get Sudowoodo up a little more. Other than that, seems good.
Now, counters to his Pokemon:
Gyarados: Use your Raikou. That 4x weakness to Electric will likely mean Gyarados goes down in a single hit to either Thunder or Thunder Fang. Not much of an issue.
Aerodactyl: Gyarados or Raikou is the way to go. Both Electric and Water moves are super effective. If you use Gyarados, be mindful of super effective Rock Slides and Thunder Fangs coming your way.
Charizard: Here's where your Sudowoodo could come in. While it is likely slower than Charizard, it can do serious damage with its Rock-type moves, and Charizard likely can't do too much in return.
Dragonites: If you fancy a slightly risky play, Gyarados's Blizzard will likely end them all easily. However, this is unreliable, as Blizzard is not a highly accurate move. If you use Gyarados, be mindful! One of the Dragonites has Thunder. Try Sudowoodo, as Rock-type moves will also deal super effective damage. The rest of your Pokemon seem like they could dish out solid neutral damage as well.
Hope I helped, and good luck!