Here's what I'd do:
I'd write out on a piece of paper all the activities, and what I'd allow myself to do.
1) Food & movies. - I don't need food to watch movies nor to enjoy my friends' company. So I'd just hang out and watch with the gang.
2) Pizza - A slice or two of pizza would be okay, but I'd be getting myself a small salad to go along with it to fill me up.
3) Ice cream - This depends. If it were my favorite local shop, I'd indulge in one scoop of my favorite flavor. If it were just a Baskin Robbins or Carvel I'd pass without a second thought. If I'm going to have ice cream, it should be the best. I won't waste calories on stuff that isn't superb.
And yes, that sounds food snobbish, but I have to be if I want to balance out whether something is worth the calories or not.
Lastly, I'd enjoy the walking. I'd take a couple extra steps. Or make an excuse to go the long way around the building. Anything for a little bit of movement.
Enjoy the day! And focus on the fun!