Helping children cope with divorce

How can I help my teens deal with the fallout of my divorce? It's been painful for everyone, but I'm especially concerned about my oldest son. Ever since my ex-husband left a year and a half ago, he seems to be putting himself under a lot of pressure to assume the role of the "man of the house." This is especially difficult for him since he was looking forward to going away to university next year. Now he feels obligated to stay at home and help the family. What can I do for him and the rest of the kids?