Woah!! This is out of hand!
All your kids are nursery age and you’re getting this wound up already? Easy tiger! Pace yourself or you’ll never manage primary school let alone secondary and teenagers!
The kid is 5 and clearly has invited his best friends, he hasn’t stopped to think about the wider political side of all of this, because he’s a pre-schooler.
Agreed his mum has dropped a ball here, and should have reserved a place in the party for your ds, but taking nuclear action like this over a kids invitation is bonkers.
Your ds is unlikely to register/give a shit, and that’s 100% within your job description to manage
“As lovely as it would be to be invited to everything, sometimes it doesn’t happen, but that’s ok”
Or you very slickly arrange for you and your kids to do something else and then technically you’re ‘busy’ doing something funner
Don’t be a bitch about this, don’t do the passive aggressive crap with poncy guilt tripping texts messages, just accept it for what it is - an oversight - and move on.