Have done it and can say that it is a challenge.
Advice is
Get dedicated drivers if you can
Sleep when in the bus - you will need it
Eat plenty
warm up before you march off into the hills- one of our team didn't and ended up in agony on scaffel
I would advise doing scaffel from the Wasdale head side
Make sure you fill up with fuel before you go to do Scaffel, we didn't and had to drive all the way to the motorway on the red light and just got to the service station as the van started to cough,
there aren't a lot of garages open on a friday night on the route out from the hills
Make sure you are well up on your navigation Snowdon at night is completely different mountain to daytime
Although its a challenge it is worth it for the sense of achievment. I am proud to say that i have done it.
I am thinking of doing it again next year