I know how you feel and how hard it must be for you. I too dreaded moments like this and luckily they have been few and far between.
I still have to clench my fists and grit my teeth when ex and bimbobitch drop the kids off on a sat sometimes and have to listen to her talking to the kids when all I want to do is leap over the hedge and rip her throat out
like others have said, I would go too, stand with a few friends as far away as possible, hold your head up high and pretend you really don't care (easier said than done I know)
good luck