Hi and welcome! I am sorry about your son's recent diagnosis. I think it is wonderful you've joined the forum for your son. You'll learn so much from those who deal with Crohn's daily.
There are many different treatment options. Unfortunately, there isn't a miracle drug. Some meds work well for one person, and not at all for another. It can take time to figure out the right treatment plan. What direction your son's GI decides to go with depends on your son's disease location and severity. If your son's disease is considered mild to moderate, his GI may start him on an anti-inflammatory called 5 ASA's (ex: Pentasa, Lialda, Asocol). These drugs are considered mild with little side effects. He may also put your son on a course of steroids for a few weeks. Steroids should help immediately giving the maintenance drug time to kick in.
However, if your son's disease is more severe, his GI may suggest starting him on an immune suppressant (6MP) or biologic (Remicade or Humira). These drugs are used to hopefully calm down the over active immune system. Of course, there is a concern of increased risk of infection or even cancer with this type of drug. However, the risk is very low, and with severe disease, the benefits of these drugs greatly outweigh the potential side effects.
Of course, as Dusty said, there are diet & lifestyle changes that can help, as well. Sometimes a combo of traditional meds, diet, and lifestyle changes is needed. It all depends on the individual.
Do your homework and write down your questions, so you won't forget anything. Good luck and let us know how it goes.