That sucks.
All I can suggest is that it's through the good times and the bad, that you find out who your true friends/family are (and what kind of friend or family you are).
Maybe it'll be a "blessing in disguise" so to speak....To have a celebration free of all that jw toxicity.
Any reason why your son isn't picking up the phone and extending the invitations personally? If he really wants to honour them with a place at his celebration and these people ( "family" ) want to opt out, I think they should have to do so personally instead of everybody hiding behind you (or your beautifully crafted invites.)
When I graduated high school, I was a witness (in "good standing") though in a congregation that encouraged homeschooling and dropping out in Grade 10 to pioneer. Although I wasn't the only one to push through to Grade 12, I may have been one of the few females to do so and must have been the only one to "dare" to want to celebrate the accomplishment. (It felt very much like a celebration worthy accomplishment at the time, having worked 2 p/t jobs and auxiliary pioneered through much of it). I was careful to avoid the "worldly" "revelries", and planned a private dinner to celebrate the occasion with my family and friends. I personally and directly invited those I wanted there (by telephone).
When I invited one of my most beloved (JW) friends from high school (he had graduated a year ahead of me but prior to that had been a big part of my high school experience/ daily life), he declined, explaining that he had been told by an elder in the hall that if he attended my graduation celebration, he would not be considered for the privileges he was working toward. (He was pioneering and wanted to be an MS). I knew my friend's dreams well enough that I could empathize with his political predicament. His candor made it easier for me to shrug off my disappointment and respect his choice. People make choices. That's the beauty of free will.
The dinner was great because of everyone that went out of their way to come. Those who didn't were ultimately of little consequence, even though I loved them and had invested some of my life energy into them (and they into me).
Spilled milk. Cry if you must and move on. Sounds like you've got a party to plan. I hope you are getting your sleep, it sounds like you've been very busy lately, momma bear!
Congrats to your son on reaching this milestone! :) What's he doing next?
It sounds like you go to great lengths to be supportive of your kids. That kind of love from one person, matters more than all the people that for whatever reason don't step up.
Good work momma.