Good evening Charlie and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
It’s working fine when the customer first places the order, but if they update their basket they aren’t asked for the extra attendees.
You are absolutely right. For technical reasons, for now the plugin is unable to capture additional attendee data during the cart phase.
We are currently repairing an extension that would allow you to add and edit data. You will be contacted as soon as it’s released.
In the meantime, the simplest solution is to prevent quantity change on the number of tickets in the cart page. It’s less than ideal, but it can serve as a bulletproof workaround for now.
You could apply the following snippet in the functions.php file of your theme (without the PHP tag at the top): https://gist.github.com/elimn/ed648363bbac1061e37bdbf7ecb720b3
But first to be extra safe, before making any changes to your functions.php file, you should make a backup of that file.
Let me know how that goes.
Best regards,
Geoff B.