While this is very sad for you, please re-read what you told us:
"I let her know that she shouldn't worry about me, as I did none of the raising, and it was really her mother's day to savor."
Can you see how she and the whole family interpreted that as "Don't worry about including me"? We don't know the whole story of what sounds like a very negative set of family relationships, but since you say "I was not welcome to participate in religious events around [the grandchild's] birth" and "my husband had from the outset taken my non-participation for granted," it's clear that this should not come as any surprise to you; you have been excluded in the past from other major events and your own husband assumes -- without any apparent contradiction from you? -- that you will be excluded, and he seems to be fine with it.
He is probably relieved. He does not have to fight or argue with anyone on your behalf. His inaction is sad, and I see why it wounds you. But have you told him, now or previously, that you would like to be included and want him, as your husband, to see that you ARE included in such events?
It seems that you have a pattern, before this wedding, of being excluded by them, which is their fault and their loss. Your husband has a pattern of being a wimp who doesn't stand up for you or even at least ask someone if you can be included, which is his fault. But if you have not, before this, said clearly and unequivocally to anyone in your family -- husband included, "I would like to be present at this event because I am part of the familiy and feel very hurt when I am excluded. What role can I play here? What can I attend in a way that will include me but not alienate you?"....if you have not been clear and stood up for yourself in that way before this wedding, why would they make an effort to include you now?
I don't mean to sound harsh and we dont' have all the details in this post, but just going on the post, it sounds as if your early message to "not worry about me" was taken by everyone else as "It's OK to leave me out." You did not intend that , but since the family has a past history of excluding you, that is exactly how they took it -- and it should not be a surprise.
Have you gotten any counseling, either as a couple or by yourself, to deal with these very acrimonious relationships? You say you're "falling apart" at the rejection but again - this has gone on prior to this one event, right? Why put so much emotional stock in what these people think of you if they regularly exclude you? A counselor could help you figure out why this means so much to you and why you have not stood up to them sooner.