Excellent article in the link...
With regard to the 'sensitive' nature of the whole thing I would imagine an approach by the Club would receive a favourable response as it would imply an organised event involving responsible people rather than something all together more antisocial??
I would hardly imagine anyone baulking at the spectacle of a bunch of middle-aged enthusiasts engaged in a colourful and slightly painfull day out compared to the hundreds of Hikers every day of the season...
I think they expect a bunch of riders at the afternoon watershed to be waiting to go up. The morning ride at dawn in summer I would love to do - as the descent down Telegraph isnt part of the ban it gives you a bit more time to do the ride. Also the Ranger path isn't nearly as well used as the railway path so going up next to the railway at dawn would mean you see very few people, then descending down Rangers/Telegraph when the walkers start to go up would be ideal.
Informing the authorities beforehand would be a great idea - reassuring them it is well organised with 1st aiders and qualified folk, plus that we wouldn't be racing or careering down on DH bikes would be a great thing, and show a lot of respect for the tough job they have to do.
A big group waiting at Llanberis at 5pm would be conspicuous. Chasing the light at the end of the day on a big mountain isn't something I like - if there is an injury or severe mechanical I'd rather be breaking the ban in the morning (which if there was a problem I am sure the local park rangers would understand) than have the darkness descending upon me with a broken leg or a snapped frame.
If you've not been up before don't think it is in any way easy, just because there is a railway. It's a long way to go up, and very technical/rocky on the way down. If I did it I would certainly be finding myself some suspension forks for the RM - just to help with arm fatigue or crash avoidance rather than to be able to go faster.
BUT saying all that, if you are on the top on a clear day it is one of the best views in the UK, just stunning, and worth every problem you may have to overcome to be able to get there.
Lets DO IT!