I have a parent form that creates one to many children items.   The child item has a workflow that starts when the item is created.   The problem is, the child needs to wait for the parent to be saved.   What is the best way to do this?

Thoughts I had

1. Simple solution.   Just delay X minutes when the child workflow runs.   The problem with that is I might wait needlessly long or not long enough.

2.  Have the parent update a flag on all of its associated children.   Then have the child workflow wait for that flag to be set.

Are there any other ideas?