So here's a question building on that: if you move the parent's due date earlier than the child's, what should happen?
- Silently "clip" due date to match parent's (current behavior)
- Issue a warning that a child's due date will be invisibly adjusted
- Alter child's due date to match parent
- Crash and delete sync database :-)
Of course, there may be many affected children, which means any warning is probably going to be something frustratingly vague like the one you get when you try to delete something with hidden actions.