How dare you start an IRA for your kid thread. Now less people will look at the one I started!
Having said that, do a Roth, not a traditional, IRA. The Roth allows him to later take it out without paying any taxes. If it's $5,000,000, it will be tax-free.
Also, don't do IF he will. Just make him because that's what working people do. If it's just something all working people do, then he'll be more inclined to just go with the flow. Or you can have a meeting where the financial advisor shows him the chart that shows him that his little bit of dough will be a lot, and he'll be like "well, I have to. It's too much to let pass by."