What is the best way to implement edits/undo's for parent/child records?

We have an edit form that allows editing of a parent record, and shows a list of the child records. Selecting a child record brings up the edit form for the child. We would like the CANCEL button for the parent to not only cancel parent edits but also child edits.

Our thought was to begin a transaction on the main form, and begin a nested transaction for the child form. Cancelling the child would rollback the nested transaction, while cancelling the parent would rollback the parent (and effectively rollback the child changes).

This would seem to work well, except that the parent and child have private data sessions, so they don't share transactions.

Should we have the child use the data session of the parent, or are we going about this wrong?

Bob