I've always loved Halloween - it's my favorite holiday- which can be complicated for us T1s. Here's the things that I suggest to you to hopefully make it more managable. These are things that I've tried to do. You can take em' or leave em'.
First, make it more about the other parts of the holiday as much as you can. Get excited about your costume. Watch scarey movies. Tell creepy stories. Try to jump out and spook your friends . . .
Second, you know you are not going to eat just one piece of candy. No one does. But, if you can set aside a certain amount ,maybe 6-10 pieces, and that's it for the night. Put the rest of your candy somewhere else, so you don't keep sneaking pieces. That way you'll be aware of what you are having, at each point and over the night.
You can count the carbs up front and bolus for them all. It sounds like you are on shots (?) so that makes it trickier. Depending on what kind of insulin you take, you know when it starts to peak and when it is finished. Try to plan when you eat your candy around that timing. (Although I know it's hard to do). Also, if you are walking a lot, you might get low and be lucky enough to have some candy right there to treat it. ;)
Third, make an event out of the candy before you start popping them. I know my friends and I used to dump all our loot out on the floor and then trade to see what we could get. I always thought this was a fun thing to do. (I know, I'm a little weird.) My friends and I used to also play a kind of truth or dare with the candy. Ex: "I'll give you this snack size snickers and a blow pop if you tell us who in our class you like." Again, it gives you something to do before you all start stuffing your faces. :)
This also gives you an opportunity to decide what you really want to have, what you don't really want at all and what you might want to save for another time.
Fourth, I'd say that if you are going back to your own house, or your friend's house, make sure there are healthier, low carb snacks there. Veggies (I know, who wants that on Halloween?- no one.), pretzels, sugar free jello or pudding, etc. It sounds lame, but sometimes people do pretty creative things with the food to make them Halloween festive. :) If you know that you have these things back at home, you can still snack with your friends without your sugar going crazy.
Finally, test frequently to see where you are at and what you are eating is doing to you.
Hope this helps. Good luck with the holiday.