If they are being strict with not giving away free food, and the computer system has not be updated (or won't be) to purchase extras, then they likely can't input on an order anything other than substitutions or things like "no onion".
You mean in lieu of the prix fixe? I don't think that will happen especially with characters.
If you just mean ability to purchase extra ... if they were smart they would work on the menu & computer system to create add ons at an additional charge so folks can add to it. OR for some extra value maybe add a fruit tray along with the pastry basket. Then perhaps drop fruit from menu and add something else.
All you can eat means a lower quality food, service and venue. This is priced for better cooked to order food, a true server and character interaction in a lovely upscale venue.
But I agree, glad if they are now operating how they set it up, how the menu states and what prix fixe means. For folks who want the nicer venue, characters and better food they might have a chance at eating there. I don't think they'll have any trouble filling seats.