OP I'd let your son call him. If he answers let him and your son talk. If he doesn't answer your son can leave a message, and you can reassure him that he WILL get to school even if you take him and he'll see his dad at the weekend.
Don't make any excuses for him, as hard as it is to see them upset. A simple "I'm not sure why, you will have to ask your dad." In a kind voice, followed by some reassurance that you will take him to school/pick up the slack.
Replying at 1am, I think other posters were right that he was out drinking (or shagging). 🙄
I saw your comment about sending food.....
If YOU had no money for food, what would you do? Personally as a parent I'd:
- try to avoid the situation to begin with (eg by not spunking money on gym/tattoos).
- sell ANYTHING I could to buy food (old dvds, old toys, old clothes).
- ask my bank for a temporary overdraft with a plan to reduce it back gradually.
- go to a food bank or a community pantry.
I'd do ALL of those things before making it anyone else's problem. And I have done all of those things in the past btw. Only had to use a food bank once in 21 years of parenting but yes I did swallow my pride and get food from there for my child.
A responsible parent tries to always have food for their kids and if times are genuinely dire then there is help available.
It is not your problem to solve.
I would suggest instead of sending food. Or nappies. Etc is that if he says he can't have the kids as he doesn't have the basics for them that he doesn't have them. 🤷 And you log it that he didn't have his scheduled time as he couldn't feed/clothe/provide nappies etc for them.
If he hadn't spunked hundreds on a tattoo I might have a little sympathy for money being tight but he's a selfish man child who can't budget his funds with his children in first place. 🤬
I know you've said before your natural instinct is to help/problem solve and I know that will be hard to step back from when it involves your kids. But the solution is to let him fall. He will either miss the time with the kids and get his act together or he won't. Either way the kids will be fine as they have you being responsible and putting them first.