One option - among many others - would be random samples to send the invitatation campaign in batches, preventing peaks of web server activity.
A possible campaign could consist of an email containing a link to a landing page which in turn would have URL parameters with the data you would like customers to update.
The landing page would collect those URL parameters, populate the fields and then give customers the opportubity to amend any data.
Pre-populating email address in subscription forms through visible fields