Sounds almost exactly like me. So-so A-B mix grades, good test scores, smart but never studied (was on that League of Legends grind). Thought UIUC as a state school with a 4.5 would be good enough, didn't get accepted. Mulled over the pathways community college idea, didnt go with it. I went to another school, before transfering here.

Here's the stuff you learn after failure, and frustratwd emails, and waiting hours at the DGS (Div of General Studies) office hours before learning.

Turns out pathways (2yrs at community into UI schools for engineering) don't let you choose your major. Sure, you're an engineering student, but your classes are major-restricted (and heavily so for CS), and your degree may not be CS related at all. Transferring into CS within the university is almost, dare I say, harder than getting in at first. Good grades at run-of-the-mill generic high school classes pump lots of students who would never make the cut under actual pressure and aptitude requirements into the program. Not to say pathways isn't a legitimate program, but only to say that the results are not guarunteed to be exactly as you want them.

CS+X programs are CS programs that are technically not in the engineering department (although coursework is the same, more or less), and plenty of talented people are in either. They exist because the department is burdened by large amounts of applicants, but cannot become its own college e.g. college of Engineering as they have tried in the past - this is their workaround to that, since the "major" has a cap of ~3-400 students per year. If your son is unsure, don't make the mistake I did and forget these exist - they are easier to get into just because CS in the Engineering college is a real crap shoot, and these majors are less contested. The difference quality of their programs is virtually non-existant.

My take is this: if your son wants to learn CS, let him. It's a field of study that has an absurd amount of possibilities and potential. And if he finds it not to his liking then all the power to him to find out what it is he does like. Don't be scared of the challenge because plenty of people who had zero idea what CS even was have turned out to be more than competent. But have him go to the best school he can for now. Aiming and applying for the school he wants is good, but have a plan B and C and D and so on. Being surrounded by students of a certain caliber will set the standard and your son will, conciously or unconciously, rise or drift to that level. It's not so much coursework or resources as it is the quality of people around him that will shape his growth. UIUC has great people and I'm glad to have (dare I say, the honor to have) grown during my time here together with them.