Will a delete then insert within a transaction cascade?
I'm only familiar with SQL Server:

Each operation is atomic. If you run a delete, and it cascades to other tables, those records are gone, too, as soon as the statement is over. They don't magically come back into existence unless the transaction is rolled back.

If you're relying on the ID values and don't want to cascade the related tables, consider switching to a merge strategy (where you use UPDATE or, preferably MERGE) instead of blowing everything away and starting from scratch.

I suppose you could try something like disabling the relationships during data loading, but given what I think you're trying to do, that seems fraught with peril. Definitely try a merge strategy first.