I think you've got the right idea now ? No matter what date someone can't make it so stick to that, and make plans for where to stop along the way to meet up and pick up groups of people and their respective times.
For example, North of Boston people can meet at North Shore mall or Square One somewhere...etc.
North shore would be the optimal final meeting place most likely.
Need to take a look at an interesting route to get up to Mt. Washington.
For the folks coming from the south/west/etc - let's meet up at the Solomon Pond Mall - it's right where 290 ane 495 meet so it's fairly centralized. Then we can meet the rest at the North Shore stop.
I'll be meeting up at the Solomon Pond Mall since I'm only 30 minutes away. We need to figure out some times when we're planning on meeting at the different locations.