It's OK. Keep breathing. Stick with the order. If, after a few weeks of no-shows, he suddenly shows up wanting to see them, tell him you will see IF they want to go (they may not and I wouldn't force it after he's been neglecting them), and IF they do, he will have to wait out in the car until you get them ready because you aren't going to have them packed up and ready to go week after week when he doesn't show up.
It will be OK, really. I'm sorry the kids are being used this way but it sounds like you are handling it beautifully with them.