I personally wont suppliment my diet for anything. I know that for me, if I start eating again then I will find it extremely hard to go back to just the packs and I will not jephardise (sp?) that for anything.
But then, I'm not you so you need to do what's best for you.
Wots the point of going if you can't eat? Well for one thing there will be lots of people there and you might have a laugh. I know that this is a biggy for me too but social occasions are about everyone getting together and the food is a side issue.
I have managed to go to a number of BBQ's now and if there are enough people there then they don't notice you haven't eaten anything, especially if you nab a soiled plate and wander round with that or leave it in front of you.
You can have a pack before you go if that will help or you can save you packs for when you are there. Maybe do a bar or cook a muffin or crisps or something.
Resisting tempatation and dealing around your feelings around food is the biggest part not only of losing the weight but also in keeping it off.
There will always be an occasion/excuse to eat.
Doing this diet is one small part out of your life to ensure that the quality of the rest of it is soooooo much better.
So my advice is to stick to the diet