If you and your son have the open, communicative relationship you describe, I certainly would not compel him to attend counseling groups. However, if you could find a support group designed for kids who have lost family members, I would make the sacrifices necessary to see that he could attend. Emphasize to him that these groups are not therapy sessions where kids see a shrink. Rather they are peer support groups facilitated by a professional.
Moving through the continuing grief that he (and you) will suffer knows no pat formula. Dont be surprised if his current coping skills break down unexpectedly. Pretending that nothings wrong by never talking about ones feelings is not healthy. At his age he may feel its his responsibility to act like the man of the family, showing you no behaviors that would trouble you. I would be concerned if he never shares any talk of his father with anyone. As long as you feel that he has outlets, through family members and friends, to express his feelings regarding his dads death and its aftermath, then you can take comfort.
There are many ways of keeping loved ones memories alive; you two need to consider ways to keep his dad remembered and honored. Creating rituals and occasions that accomplish this is a priority. Please write me any time you think I could be of help.