We did have Monitorama here before (which I sadly missed) - probably would draw a similar crowd?
+1 DevOpsDays Boston.
Ideally avoiding the monitorama PDX date.
+1 on the willing to help as well.
And can probably gather a few volunteers for the event day as well.
In terms of Venue, the NERD center is great for meetups, but can it hold 300-400 people? I've only been to events with ~100 before. Also, parking would be difficult/expensive in Cambridge during the day.
I maybe able to help with the venue. I've never attended a previous DOD. If I can get an idea what's needed (e.g. headcounts, equipment, food), I can help find a place.