You know, it's ok if you don't want to attend. But be careful not to put it on your son's shoulders. You shouldn't make him feel like he has to choose.
I'm reminded of my ex's family. His mom was the WAS. Her new husband was not the OM, thankfully. The three boys were estranged from her and all married without inviting her. One daughter was dependent upon daddy paying the wedding bills and didn't invite mom even though they were not estranged. When second daughter married she put her foot down and invited both parents; if one or the other didn't come then fine, but she refused to be put in the position of having to choose. (Both came and it was ok).
Just don't put your son in the position of having to choose. Bow out gracefully, let him know it's not his fault but that you're simply not ready to do that and would be too uncomfortable so you're going to skip the event. Offer to take him and DIL out to breakfast to celebrate on another day. Do NOT make him feel like he has to choose.
