The -mas suffix indicates Mass in the Christian sense, as you might have expected; so yes, it has definite religious overtones. It's not completely inappropriate if you dig deep enough into the etymology (it suggests a mission; spreading the good news, so to speak), but I'd expect relatively few people to do so.
Part of the advantage of Newtonmass is that it's a sufficiently clever joke (IMO anyway) that it becomes less about sending up Christmas than the double meaning of "mass." Or at least it can, if you explain it right.
Regardless, I don't think either Baconmas or Newtonmas or Newtonmass are actually all that offensive. My suspicion is that the sort of Christian who would get annoyed would also be annoyed at the range of politically correct holiday greetings that explicitly AVOID mentioning Christmas at all, so the reference builds Christmas' importa...
The Gist: I started this blog to get people excited about a science-themed holiday. I want your suggestions before I advertise it to everyone I know!
Two years ago, I came up with the idea of celebrating Sir Francis Bacon's birthday (Jan. 22) as a festive science-themed holiday called Baconmas. (The name has the additional bonus that it's easy to convince people to come to a party if there will be bacon there.) I had a good Baconmas party in 2010 and a better one in 2011, and now I want to let other people in on the fun.
So I made a website.
It's currently "in beta"; I wrote a couple of preparatory things, but haven't yet shown it to the vast majority of my friends. I want to maximize the chance that it goes a bit viral when I do, because a science-themed holiday really needs to exist. So I'd like any suggestions you have, before I go "alpha" with it. So as to not cause anchoring, I'll put down in the first comment the things I already plan to do- if you could make all your original suggestions first, then read those plans and others' comments, then add more suggestions, that should maximize the good ideas. Thanks!
(Oh, and it goes without saying that you should celebrate Baconmas if at all possible. It's been a lot of fun for me.)