Me personally I choose to avoid all contact with them once it is over, especially if they are actively using. It is not that I have an emotional attachment or hurt to work through with them, it's just a choice I make because I know being around them would make me feel uncomfortable. I had to teach myself to make this choice a conscious one--boundary work, no more, no less. You may find that you go and have a great time and don't feel uncomfortable. Or, you go and feel uncomfortable and just deal with that, confident that you can CHOOSE to take care of yourself in whatever way is necessary.
I know you'll make the right decision when the time comes
