Okay, I have some suggestions for you. EV spreads are up to you.
Vaporeon: I took into account that it was on your team originally, so I made sure to steer clear of egg moves.
-Surf
-Ice Beam
-Signal Beam
-Hidden Power: Electric/Toxic
If you have Platinum, you're lucky. We can check Hidden Power types, now! In Veilstone where you get Game Corner Prizes, talk to the guy in yellow hair. Don't forget your leftovers on Vappy!
Flygon: Be sure to put a Choice Scarf on him (if you want). That way, he'll be a devestating revenge-killer in late game.
-Earthquake
-Outrage/Dragon Claw
-U-turn
-Fire Punch/Stone Edge
U-turn is bound to go first if you have a Scarf on. It will help you get away from opposing threats. The Dragon/Ground/Fire attacks will hit everything in the game for AT LEAST neutral.
Meganium: Not a bad choice, here. I quite like the idea, actually.
-Energy Ball
-Aromatherapy
-Leech Seed
-Light Screen/Reflect
This is a support Meganium. Leech seed is great against opposing Poké's that are walling you. Choose Light Screen or Reflect according to your team's needs. Aromatherapy gets rid of all status of your entire team. That SHOULD be there.
Charizard: Seeing as how you bred one with Flare Blitz, I chose a physical set for ya.
-Flare Blitz
-Earthquake
-Focus Punch/Rock Slide
-Dragon Claw (?)
Instead of having either Focus Punch or Rock Slide, feel free to get rid of Dragon Claw for both of them. Focus Punch hits hard if you can predict a switch.
Lucario: I see you only have Vappy and Meganium as possible special hitters (other than Lucario), so I looked up a special moveset.
-Aura Sphere
-Shadow Ball
-Vacuum Wave
-Hidden Power: Rock/Ice
If neither Hidden Powers are available to you, Flash Cannon is always a good STAB (same type attack bonus) move to consider.
Nidoking: Not the heaviest of hitters, but such a diverse movepool can also prove to be fatal.
-Earthquake
-Stone Edge
-Megahorn
-Sucker Punch
Remember, these are just suggestions. You can do whatever you want. Have fun and good luck constructing your team.
Hope I helped.