I think the fundraiser month should be a month full of activity on DC, with contests etc., that will (hopefully) inspire people to donate. Not just a month where we ask "please donate". I think publicly setting a goal amount is not necessary or even harmful. App's idea of a survey sounds nice.
If the month will include coding contests, these should be announced well in time. Personally I would like to see an announcement about two months before the deadline so I can plan enough time to work on it.
Don't know if December is a good month. In a way it's great because you can also do a "year in review". On the other hand, people may be busy or short on cash, as was said. For me personally it's a busy month so for a contest, I'd prefer another month. On the other hand, NANY worked out fine last year because there was more time before the deadline.
Maybe it's a good idea to set a DC "calendar" each year (maybe only visible to people who are interested) with deadlines, contests etc. to make things easier to plan.