You cannot magically make it happen in less than a minute, if you do it synchronously, calling the web services is the best option, otherwise asynchronously but it would take even longer. As you noted, changing in DB is not the correct way because it would
bypass all the cascading rules and data integrity can be compromised.
Is there a way you can modify the requirement to allow for more flexibility? Such as doing one business unit at a time, for example.
Gonzalo | gonzaloruizcrm.blogspot.com