Update: he was 15 minutes late this morning, i did not yell at him or call him names, i said that when he is late i can not pump milk for son 9 months,.
This was very good--not only because you didn't yell or call him names (I imagine you know that is never a good idea)--but you explained the IMPACT of what his being late means to you and your children. In a warmer friendlier voice....say it like you would say it to someone you're really close to. That's all you really need to do. Then drop it. And watch his behavior in the next few times after. It doesn't mean he won't slip up, but he might make an effort next time.
