I grew up with 2 parents who made false promises and couldn't commit to what they had said. It was utterly devastating. I will never allow my children to experience that. Letting him fail on a birthday party for my children would be failing my children as their mother.
And before everyone calls me a martyr.
I will always be a bloody martyr if I have to than disappoint my DC because their Dad is delusional.
But you have no idea if he would have 'failed' because you stepped in and stopped him doing it HIS way which yes, may be very different from your way, but will still be valid. Children do not need a father who is like their mother. They don't need everything to be done only one 'perfect' way.
Would you agree that it is you that has the worry and fear about failing because of your own disturbed childhood, and that it is you that is stopping your DH from engaging with, and parenting his DC because of this?
Your fears are stopping you from being able to function and co-parent with your DH. He is being disengaged from his children, from his role as a parent.
He feels depressed and longs to to try some things like a FAMILY HOLIDAY ABROAD which you say is not possible AT ALL because you found it too stressful. But do you see that your need for it to be done the 'right' way is what made it all so stressful?
Children who never see things going wrong in a safe family environment will grow up anxious and without having learned that they do, after all have the resources to cope with the mistakes and bumpy rides and the less than perfect.
This is why counselling would be so helpful for both of you. You need to talk together with a really good counsellor.
I also think you would benefit enormously from single counselling - you would get such relief if you could let go of some of the massive load you are carrying all the time.