I don't have specific information, but I know that interventions are best done with the help of a professional who can keep the emotions of the people involved from getting out of hand.
I'm not sure how old your son is, but he may not agree to this. Or if it is a surprise, he may just walk away from it and leave you all sitting there.
Although I think interventions, properly done, may sometimes help the process, in the end it's up to the addict to reach out for help for themselves. We can't make them get clean, oh God how I wish we could.
Others may have more and better information, those are just my thoughts and may or may not apply to your situation.
My prayers go out for your son and your family.
Hugs