Gordy, I can't help you directly with this one. I guess you just have to publicise it well.
I organised Bike Week events for Greenwich Cyclists one year. Its hard work, but worth it. One good idea I came up with was the "Tour de Greenwich" - a fun day out on the bikes, where I thought up several "stages" which were fun races or events at various points round the borough. We ended up with a quiz in a cafe.
I would recommend something like that for a general Bike Week event - but just don't let people get carried away with the competitive spirit! You want to stage a slow race, not some downhill sprints!
For the Bike to Work event, how about organising some races round the car park? Might encourage people to dig those bikes out of the shed. Or get a local cycle shop to send along a mechanic for a Dr Bike session. Though that presupposes that the bikes are in a fit state to cycle them to work in the first place. Thinking again, how about a pre-Bike Week Dr Bike session - bring in your bike from the shed and it will have tyres pumped up, gears adjusted etc. in preparation for the big Bike to Work?
Or another thought - people these days go on about carbon footprints. Work out the carbon footprint for a typical journey to/from work, and make people feel good about reducing their carbon footprint for that day. (Yes I KNOW it will be minimal, but you have to make people feel good about themselves).