Not knowing all the details it is hard to really comment much about the snub. I am not sure how long you have been out to them, but from my own personal experience some people need a "lot" of time to come to grips with the whole situation. I personally, based on your short explanation above, would write it off for now, maybe talk to those who went anyway and then come to terms with the total situation. I also would not expect someone to not go because I was not invited, unless it was a very personal and important occasion, and even then I am not sure what I would do.
I was supposed to go to a wedding of a close friend of my daughter in Cancun, Mexico, and I was invited to go as Allie by the bride to be. However, after almost a year before the wedding, my daughter was apparently making a very big deal of Dad going to as a woman.. I got into an argument with her in March of last year, didn't go to the wedding, everyone else invited went too, and I didn't talk with her until last Thanksgiving when she was coerced by other family members to invite me to dinner as myself. So, in my case I dealt with it, suffered and am now precariously on the road to better relations with my daughter. I hope that helps you. Please let us know what you feel now.