DS18 is due to go on his first (and only) school/college trip to NY in December. The trip came up in January. Through txts, Dad and I agreed to split the installments between us so that we would end up paying the same amount, and DS would pay the remaining amount (he has a part-time job and has saved up, bless him).
To provide a short background, his Dad and I have long been separated: DS lives half with Dad&SM and half with me/OH. Because Dad's half-week is Mon/Tue, Wed, Thu, I still pay a large amount (over what I should) to him in child support* every month.
Anyway, I've paid my two installments, but Dad has not paid his. He missed both deadlines for his two payment installments. When he missed the first one I questioned him about it (through txts) and he fobbed with off with some guff about paying it, but the payment not registering - when I phoned the college they confirmed that this was not true: Dad hasn't paid his share. The trip is now six weeks away and there's a large outstanding balance still to pay, meaning DS might not get to go at all. Do I confront Dad again (this never ends well)? Or do I simply stop my child support payments* to Dad for a couple of months (they are not court-ordered) and pay the balance of the NY trip instead?
*I understand that I must keep paying child support until DS leaves full-time education and I'm OK with that; however, Dad doesn't pay for DS’s meals at college, buy him clothes or shoes, textbooks or college fees (I had to pay them last time). Additionally, SM asked me to contribute half the cost of DS's bus pass (which I agreed to), and I provide DS with a small allowance each month. DS lives with me for half the week and so Dad & I are equally paying for his room & board, food. I think I do all DS's washing, he seems to bring it all with him on Friday from his Dad's. Dad recently bought a brand-new Lexus so I know he's not strapped for cash. I don't feel at all inclined to simply pay the rest of the money for the trip on his Dad's behalf, without taking it back in some way... but... AIBU?