I'm a snowboard instructor as well and my son is now 5. He started boarding at 4 and out of experience I can say, that it is very hard to teach kids that young any specifics. Last year, he didn't understand heel or toe traverse at all and just went straight. This year was way better. He now can do heel side and straight to a T, combined with a few jumps and tricks and butterboxes. Just let your kid have fun. Teaching him the breaks is the most important, the rest will fall into place. My little guy didn't even understand how to break last year at all. He just went straight and fell on his butt. So yours is pretty advanced at 2.5 with knowing this, I'd say.
Just have fun with him and the rest will develop!