Well since the world has just restarted the geopolitical situation from before WW2 (every country for themselves), how about you help your son to become a doctor? You know, a medical doctor. It will require lots of teaching.

The US has somewhat stepped out (been forced out of the arbiter role, frankly, much to everyone's delight) and this was supposedly going to be bad for the US since "everybody else will step in and get the goodwill the US gives up" ... and it's pretty clear now that in reality nobody stepped in and the animus to step in is at an all-time low and dropping further. It has to get a lot worse before we'll even consider (spending the money) to make it better again.

And, no worries! The EU will save us! Or so they claim ... what they mean is they will use economic sanctions to fix things! (They're "free", as don't require budget allocations and so no political conflicts, and very useful for political corruption). Except of course free is between quotes because there is a reason every economist hates them: they are in fact more expensive than just about anything else. But no budget line item!

Oh, in negotiation theory I'm of the opinion that economic sanctions cause wars rather than solve them. Wars are started because one party feels they can improve their economic situation through physical conquest. Add sanctions and there's two options: give in to sanctions (which means you have lost the war, and so have to give up anything the sanctioning side wants, or they'll just sanction you again), or win the war (which will give the opposing side no choice but to give up sanctions, since there's nothing to be gained anymore, and the sanctions will hurt them too). Obviously this means it's not just dictators that will react to sanctions with aggression, everybody will. There's even the problem that they may generate the worst possible outcome. Situation: 2 parties are at war. Someone imposes economic sanctions "to help", but sanctions inevitably also hurt others. Shortly afterwards 5 parties are at war. Oh, and historically economic sanctions have caused far more wars than they have solved, and have in fact dragged more countries into wars they initially didn't participate in.

So that's what the world has decided to do (not the US, in fact I would argue the US was the party that had the least to do with this decision, because the US absolutely didn't choose to lose it's overwhelming economic and military advantage, everyone else very slowly took it away without taking over security. Deciding, in fact, again and again and again, to let security slip further. This was not "a slippery slope", but governments worldwide taking vote after vote after vote to never do anything about an aggressor, time and time again. But, of course, this is not how it will be presented in the press)

Anyway back to why doctor would be good:

1) lots of them will be necessary since obviously lots of countries will be free to wage war on one another without having to face the US as well and so ... they will wage war on one another

You know, what the UN GA, and the "non-aligned movement" have worked for, for decades now. I feel like someone should walk into that meeting, smile like doctor Strange did at the end of that movie, and point out the obvious to these delegates that finally got what they wanted for decades: "Congratulations! You just got everything you ever wanted. You're NOT going to like it!"

2) the rest of the world will get more and more entangled with specific conflicts (Ukraine, Taiwan, Israel, no doubt dozens of conflicts that probably have already started but they're not on the news constantly yet ...) and will feel the necessity to "interfere", which will bring loads of countries into one war or another

This will be especially true since those countries that have started small wars are where our raw materials are mined (you know, what we absolutely positively cannot do without).

3) doctors don't have to fight, even an army in a desperate situation would be mad to send doctors to the front

4) not only do they not have to fight, BOTH sides actively avoid attacking doctors. Even hamas has shown consideration for Jewish medical facilities in their attacks.

5) oh and doctors are both an absolute necessity and the ultimate luxury in one neat package, so doctors do well during economic disaster periods AND during periods where things go well

6) it's actually hard to be a doctor, so there won't be excessive competition and your kid will actually learn a lot

7) anything a doctor does is good. It a very morally unambiguous profession, and lots of people will be forced to make questionable choices in the next decades ... and doctors have the moral luxury that they simply will do their best to minimize the impact of those decisions on actual living humans. That impact will be horrible, obviously, but a doctor can actually help