Alakazam:
Calm Mind
Psychic
Recover/Shock Wave
Reflect
Alakazam's moveset completely sucks, but it has great Sp Atk. Calm Mind boosts this even more so it can sweep easily. Shock Wave is for coverage, Recover if you want durability.
Needs vitamins for Special Attack
Gengar:
Shadow Ball
Psychic
Thunderbolt
Hypnosis
Shadow Ball for stab, Psychic/Thunderbolt for special attacks and Hypnosis because sleep is awesome.
Needs vitamins for Speed
Lapras:
Surf
Thunder
Rain Dance
Ice Beam
This way you can use Rain dance even better, while Thunder has same chance on paralysis as Body Slam!
Needs vitamins for HP
Venusaur:
Sleep Seed
Leech Seed
Sludge Bomb
Razor Leaf
Sludge Bomb is stronger than Hidden Power, the other 2 moves are nice!
Needs vitamins for Special Defense
Snorlax:
Body Slam
Earthquake
Rest
Sleep Talk
No need for 2 normal moves and Earthquake is just awesome!
Needs vitamins for Defense
You know what moves I suggested for Zapdos. Zapdos doesn't need vitamins, it's legendary already xP.
These are the movesets I suggested, while trying to keep your strategy intact, especially on Lapras and Snorlax, because they are pretty nice already :).
You might want to use a PP up on Rain Dance, Earthquake or Psychic, as those have quite low PP.
Using Rare Candies is not considered cheating as long as you found them in your game legally, either because it's in there or by pickup :).
There you go, I hope it will help you! I liked doing this, so if there's anything else, just ask :D.