You fund the kid you go without food, electricity, gas, heat, for a while. What is wrong with that notion? Your having kids with more then one people, is your own fault, now you have this relationship between kids with different parents happening. You fund this kid this one time and every other time you do not even mention where you guys have gone or whatever, until so and so complains about it.
You just do not want anything to do with the former spouse and the problem is having somebody connected to them through blood of your folks failed marriage. slow-clap-clap. Bravo.
I am person that will shutdown my life for somebody just to make sure that person has a little more life. While expending any portion of my happiness for them.
Canceling the trip is the best way because you keep money whining about this one person and your going to get played in the future when it comes around. By canceling you just ( be like "well something came up" ) could dump your kids on your ex so they could hang out and spend time, and maybe give yourself a vacation without letting them know. Or just be honest and say "I just do not have the funds" but again maybe your being cheap.
Cancel give yourself a vacation and let them hang out at their house.
Cancel and give the tickets to somebody else.
Pay fair and just be super hyper cheap for a couple of months to recover debt.
That makes everybody happy. I remember going to Six Flags.