My DH is self-employed too. If I always waited for him, there would be nights when I did not eat at all. We do not have any DC though, so there is only me to feed if he decides to work late.
For your DH to expect you and your DC to wait for him is not particularly reasonable.
Could you construct some sort of compromise? For example, I know of families where they all have Proper Breakfast together every day, in part because evenings are haphazard. Or you could, for example, agree that he will come home promptly on certain days of the week, and then be more flexible on other days, and try to have family meals on the weekend if his work allows that, something like that. Does he cook? He could take responsibility for Wednesday evenings, or Sunday lunches, or something like that, if that would work for all of you.
Waiting for DH to come home, with children who are hungry, does not sound fun for anyone, and it is not really reasonable for him to expect you to just put up with that.