The aggressive approach is more and more common with doctors and I'm told is backed up by research data, so you should definitely give your doctor's advice decent weight.
Personally, I'm a fan of the bottom up approach, which is an older approach in which you start out with less aggressive drugs, like one of the 5-ASAs (Asacol, Colazal, Sulfasalazine..) and see if those are effective (generally these drugs are not considered "enough" for Crohn's anymore, but many patients get good results from them, like me.) If your son didn't respond well enough to those drugs, then he could step up to the Remicade.
The risk of that approach is that low level inflammation may persist on 5-ASA drugs and go unnoticed until his next scope, and that low level inflammation can still potentially cause damage, like strictures and fistula. In my experience, it hasn't happened, but I'm just one example so take my story with a grain of salt.
You might also ask your doctor if Remicade without 6MP is an option, and why or why not. Even with Remicade your son should still be regularly scoped to make sure it's as effective as it ought to be. By and large, Remicade is a very effective drug for a majority of patients and it can even reverse damage suffered from inflammation before starting the drug in some cases, so it's a good option for patients who are likely to have had untreated Crohn's for a long period before diagnosis, like your son.
I hope that wasn't as clear as mud...
Welcome to the forum!
EDIT - Oh, and also... make sure to talk to your GI about dietary changes that may be helpful. If he/she tells you diet doesn't matter, I'd suggest finding a new GI. Also consider seeing a dietician. I personally have had great luck with a low-residue, no dairy diet (you can google these terms for information, if you need more direction, feel free to let me know!), but others have had luck with gluten free, modified paleo/keto diets, and the specific carbohydrate diet (this last one is pretty hardcore but there's lots of support for it.) Diet is at least as important with Crohn's as what medication you use.