Best of luck to you and congratulations on choosing to stick to plan at the indian, but I would personally have a night off plan entirely (or flexi-synning as others like to call it lol).
If I knew it was coming up, I would have minimum 5 syns on the few days running up to it, and have a syn free day on the actual day.
The next day I would just draw a line under it, go back to normal plan mode.
It is only one meal in your week, out of 21, and in my opinion with things like this it is just better to plan around it but enjoy the night as you should.