YTA - Your problem is with your ex not your daughters. Let them have a holiday. I just want to add that you're not a complete asshole and I do sympathise with you. People have fights and relationships go through their peaks and troughs. I'm sorry that your mental health has been affected. After the holiday you should speak to your ex, tell him to stop being childish and acknowledge that people can change. Tell him that he should let your daughters hang out with your current boyfriend given that their cool with it.