That is right.
Enjoy your meal and get straight back on plan and you'll be fine.
You may not have a great loss week but sometimes flexi syn days do not effect weight loss.
The important thing is to enjoy yourself and know when to get back.
Have fun!
There's no set number of syns - it's whatever you have calculated you will need to get through the occasion. That said I probably wouldn't use that as an excuse to stuff my face with the most calorific things on the menu. What you've listed sounds fine!