I am a far cry from a vet here, but I will weigh in with MO. I don’t understand the whole “I reject us and our relationship, but we can be friends forever” delusion. IMO this only delays the pain of the breakup for the spouse expounding it. That said never be mean spirited or vindictive in your communication. Be calm, rational, focused, and as kind as possible without compromising your principals.
IMO, your children and your emotions for them are being used. This should never ever be allowed to continue from either spouse.
IMO, your children need to hear you tell them how much you love and respect them. Your children need to see you demonstrating your love and respect for them. Your children need to see love and respect for your spouse during a healthy relationship. Most of us are not here with a healthy relationship. Your children do not need to see either of you being manipulated negatively or taken advantage of. JMO, take it with grains of salt.
BITS Me 55, ACK, when did that happen? Doesn't feel like 55 D 30 S 27
You create your own universe as you go along - Winston Churchill