Hi gang - we are just off the Vista so I wanted to provide an update: We did YTD with 10 people. We were able to check in on the app and got a table almost immediately every night (we did check in between 545-615 each night, so that might have helped). There are plenty of tables for ten - in 7 nights, we sat at 5 different tables.
The app does indicate that if you have more than 10 people, you have to check in with the hostess stand and not on the app. Also, you can choose which of your traveling companions are joining you for dinner each night, in case anyone was wondering.
We all decided during the day what time to meet up and where before dinner. Also - the check in and table info goes to everyone's hub app, so they will know which table to go to if they are a little bit late.
Hope this helps!