Do not react. This is one of the biggest lessons to learn in life, I think, to make you a better person. Do not let anyone else dictate your actions. Back on point- call you kids, even if it's hard to reach them. Send them letters, and occasionally presents.
Cookies are great.
One other thing you can do is to wrap your presents in your local paper. They might enjoy reading news from your home town. The adolescent years are when children make some of the most important decisions that affect their lives . Do not be fooled by their appearance, which seems very adult like. They are still your children.