Well, I'm not too good with movesets, but I'll give it a shot.

1. Blastoise - Earthquake, Ice Beam, Hydro Cannon, Mega Punch

This is a pretty solid bunch of moves; a good mix of Physical and Special attacks. I'd say leave it as is.

2. Golduck - Surf, Confusion, Water Pulse, Blizzard

This one is pretty good, but I'd suggest teaching Goldy Water Pulse instead of Brick Break - Special is Goldy's Specialty, not Physical. Besides, now almost all his moves will have a side effect - Freezing and Confusion are the best status effects, IMO.

3. Poliwhirl - Belly Drum, Rest, Snore/Sleep Talk, Brick Break

Kingler and Vaporeon are both good choices, but I think you need a Physical attacker, and when it comes to brute strength and good moves together, I'm thinking Poliwhirl. He can learn the Belly Drum/Rest combo, so his attack can go way up way fast. From there, Sleep Talk or Snore until you wake up, and for the last move, you can use a nice Earthquake, Body Slam, Hyper Beam, or some other powerful Physical attack.

Just a few suggestions - I'm no good at making good movesets either, but hey, if they get you through the game, then who cares? That's my motto (is the guy who taught his RBY Jolteon Pin Missile, Double Kick, Thunder, and Toxic).