Kids holiday contact with exh.

Kids are early and mid teens. I sent their dad a list of weeks when kids were available for contact in March, added another week and text him dates again in June. And you know, school summer holidays are usually about the same sort of time every year, right?

He has a history of not seeing them for months on end and leaving plans to literally the last minute (once cancelled as I was putting the kids in the car). Kids now travel independently to see him but I still have to get them packed up and drop at station and buy a ticket etc. Furthermore I had to involve the police with some serious allegations he made against me at the start of this year - we don't communicate other than about the kids (unless he's drunk then he barrages me with abuse)

So he calls the kids and says I can only have a couple of days off in the summer and it's on a different week to any of the dates I've given. I reluctantly agree on the proviso he confirms dates by text.

No confirmation text. And he's not contacted the kids to discuss plans in a fortnight. I've messaged twice to ask for confirmation and then to assume that as no confirmation is forthcoming to assume he isn't having them. No response.

I've been offered a friends appartment abroad but it clashes with the 2 days he has said he can have them. Kids want to go abroad with me, they've been messed about enough by him to have figured him out for themselves.

I have a residency order after much fuckwittery on his part 8 years ago refusing to allow me to take them on holiday so legally I don't need his permission.

WIBU to book flights and just go?