It seems both you and your ex have pretty specific expectations of what will happen this Christmas
You: see the kids, be a good dad while I’m here, do my best to help ex, introduce GF to family and look after myself/ rest/ have a holiday;
her: ??? Get some help from you, have the children see their father not just for xmas, but also in jan and maybe: have you around for longer to see day to day what you’re missing, who knows.)
what’s the issue here is that you haven’t really talked and compared your expectations. It’s a set up for failure (for both of you) if you both expect different things to happen without voicing them, let alone check them against reality.
it’s very hard to have those convo post separations even harder if you’re never there physically and at Christmas where all expectations of everything is heightened
i’d say be an adult, prep for an open conversation- by not being defensive and
Listen- really listen to what she says (and doesn’t say) when you ask: what’s your idea of a successful time for my visit in dec/ jan given my limited time presence and our split.
Only when she feels you have actually listened and understood, will she ever have the space to comprehend you might have other priorities…
you do need to be the bigger man here because I suspect you left her in traumatic, tragic and very unoriginal circumstances, and by the sounds of it you haven’t even really processed the separation properly if you still own stuff together like the house
if you have any hope to have a working co parenting relationship with her, the sooner you start acting like an adult by inviting open honest communication the sooner you can arrive at an actual working relationship
sadly many never get there after a difficult separation
good luck and don’t listen to any advice on here where people have reached their own conclusions of who you are or who she is without any evidence provided by you :)
they’re just projecting their stuff and ideas onto you
it seems you have guilt and shame in how you ended the relationship. It would do you well to process your stuff asap so shame doesn’t get the better of you when you do talk to your ex - some people get defensive, some become agressive, some freeze
if you’re clear on your story/ your rights and wrongs, remorses and regrets and amends made and those not made yet, and own it , you will be much clearer how to act