People grow apart, that is life, and it happens to everyone. I doubt they will think anything of your absence other then that. In fact, they more than likely will be looking forward to seeing you. Your former best friend in particular is probably wanting to get back in contact with you. Instead of dwelling on the negtives, think of the positives. It's an opportunity to rectify a mistake that you openly regret. But if you truly can't handle it, then this is the time to put the past behind once and for all.