Great! Start 'em young!
My younger son was somewhat older than that, 3 1/2, when I first took the family up right after I got my license. He's never wanted to be a pilot, but he's enjoyed flying with me off and on through the years. Hard to believe that my littlest tiny kid will be 48 in another 3 weeks, and my oldest grandson will be 9! Gawd but I'm getting old!
Here's a little story about my younger son and flying. He would have been about 5. One day while I was working on my commercial and before I was in any ownership situation, I wanted to go up and practice commercial maneuvers in a rental 172. He asked if he could go along, and of course I said he could. As we taxied out, he said, "Dad, could we do a flip?" "What's a flip?" "You know, where the airplane goes like this" as he made the sounds of an engine sputtering and then used his hand in a spinning motion. So I said, "That's a spin, and sure, we can do that."
So we climbed up to about 11,000' toward the northeast of Laramie, and I put it into a 2 turn spin. As we pulled out of the bottom, he said, "WOW! That was scary! Can we do another one?" So again, we climbed up to about 11,000', and this time we did about 1 1/2 turns the other direction. After pulling out of that one, we flew north so that I could practice lazy 8s and 8s on pylons along the railroad track.
When we got home, Wife 1 really lit into me. Turns out she was in the front yard of our house and could see both spins! Like everyone who has ever seen a spin for the first time, she was sure she was going to watch us die, because that's what always happens in the movies when an airplane starts spinning. Things were pretty cold for awhile, to say the least.
Cary