Your Lapras set is good. Keeping Surf or Hydro Pump is a matter of preference here. Some will say that it is best to keep Hydro Pump for the high damage ratio, regardless of accuracy and PP; but if you want to play it safe and still have a fairly strong move, then go for Surf. Of course, Lapras does get the attack bonus for either Surf or Hydro Pump.
For Meganium, get rid of Iron Tail and replace it with Giga Drain. There are other options available too, such as Earthquake, Leech Seed and Light Screen. Personally, I'd go for something like:
Earthquake
Leech Seed
Giga Drain/Light Screen/Body Slam
Razor Leaf
With Leftovers
Now Tyranitar... replace Sandstorm with Earthquake, and Thrash with either Rest or Ancient Power. I'd suggest AP, since you could get some nice stat boosts and cause the opponent a good amount of damage in the process. But if you don't want either, there is always Fire Blast or Thunder Bolt to use. Again here, I'd go for something like:
Earthquake
Rock Slide
Ancient Power
Rest/Thunderbolt
With leftovers
Scizor now... I suggest replacing Cut with either Baton Pass or HP Bug. If you don't want to have Scizor as a BPasser, and don't want HP Bug, then there's always Return (or Frustration) to fill in that space. As well, you could stand to lose Metal Claw, since you already have one Steel-type attack and Steel Wing being strongest of the two. So you could fill that in with HP Bug/Return if you opt for Baton Pass over Cut, or just Return/HP Bug over Cut and Metal Claw if you choose not to use Baton Pass. As with the others, attach leftovers.
Now for Snorlax... I'd suggest replacing Rollout with Self-Destruct, and replacing Snore as well. You have a few choices for that: Counter, Fire Blast, Earthquake, Curse and Double Edge. I would use something such as:
Rest
Self-Destruct/Counter
Earthquake/Curse
Double Edge/Body Slam
With leftovers
Seeing above, you have a good selection of moves to customize your Snorlax for different situations.
Now for the last slot. I would suggest a Heal Beller for this team, so putting in Blissey is an option. If you opt to do so, then you could use:
Heal Bell
Softboiled
Light Screen
Thunderbolt/Psychic
With Leftovers
Somewhat standard heal beller set.
Aside from the 2x weakness to fire, your team is good. Hope this was of any help.