I like mrsbertbibby's clear options and would go for #1.
As I understand it, the half-terms seem to be the main problem. Presumably you can have longer periods with them in the summer? I am a firm believer in quality over quantity, and since separation and having much-needed 'me times' have become so much more present when I'm with dcs. We have less (quantity) time together, but certainly not quality.
So, here's another perspective and my reason for picking option#1 (suck it up):
I could've written your post - narcissistic ex, 8/6 split in my favor plus a 5 & 6 (nearly 7) year old.
We split our half-terms differently: each week in two so one parent has a long (Fri pick-up till Wed early afternoon) and another (Wed afternoon till Mon drop-off). It also means we don't have the full weeks so don't have long holidays at half-term.
I think the worst thing you can do to a narcissist is ignore them and not show them that they're getting to you (assuming they are).
Could you just suck it up and wish them a happy holiday, and perhaps take the opportunity to book one for yourself?
Our summer holidays are split 1wk-1wk, 2wks-2wks and as much as I was worried that the two weeks would be too long without dcs, I decided to reframe my thinking around it - get them (and me) excited about it, and have had a lovely child-free 2 weeks! I should of course, mention that my stbxh will never be with them like I do and has a different parenting style but as awful as he has been, I know dcs are safe with him.
Then, I focus on my child-free time!
In fact, I think I may just stay single forever as I'm now finding my this time sacred and can't imagine ever meeting anyone I'd be willing to share that space with. I can read, have lie-ins, see friends, travel, have Netflix-filled evenings and build my business. I certainly the space to help focus on rebuilding after the financial impact the proceedings have had and continue to have!
My advice would be - take good, good care of yourself. Try to think about their time with dad differently, as long as you know they come to no harm with him. Also bear in mind that our anxiety rubs off on them, so try to celebrate (as hard as it may be) that they're off on holiday with daddy and, see how you can make their time away something for you to forward to too.
Children are incredibly resilient. As hard as these times are for them, we can also help them learn to deal with change, to be grateful and make the best out of what they have, and to learn to adapt not only to different places, but different styles, people etc. It's tough but my hope is that we are raising children that will be even more resilient and adaptable.
It's not easy and I'm thinking of you. You're not alone. This too shall pass....xx