Here is how you can do two saves in one transaction:.
(1) You must use Microsoft Distributed Transaction Coordinator (DTC)
(2) Start a Transaction (e.g., using (TransactionScope scope = new TransactionScope()
(3) Do the first SaveChanges using a Transactional Save
(4) Do the second SaveChanges using a Transactional Save
(5) If both saves are successful, commit the Transaction (e.g., scope.Complete();