I think Cal Poly might be worth a look.
It’s a very tough admit to ME (they admit by major, competing only against others who want the same). It’s a state school, so students need to be organized and disciplined to advocate for themselves. They grade very rigorously, but the environment is very collaborative. There’s no weeding out intentionally going on, but the rigor causes quite a few to change majors. The college of engineering is the biggest exporter of major changers.
That said, the Mechatronics concentration is very good. Their facilities for undergrads are spectacular with 80+ unique labs in the college of engineering alone. Although a bit over 20k, it plays like an honors college within a bigger school. All classes are small. For example, the calculus series is capped at 30 per lecture. Physics, 42. Nearly all, labs and discussions included, are taught by instructors with PhDs, not TAs. They get full theory, with no watered down math and physics, but have labs with even the most advanced classes. For example, the graduate level vibrations class has a lab, whereas the undergrad version is a lecture only class at most schools. There are many clubs beyond the usuals like SAE. Check out PROVE Lab. CubeSat was invented there and the standard and much of the launch coordination still based out of there. It’s in an idyllic location.
As I said though, students will get more automated support at some smaller privates. They have to seek it out at CP. An interesting example sticks out in my mind. My son had a pretty decent HS record. As a result, he got some good financial awards ($100k from Case and free tuition at Utah as examples). He got a little merit at CP, but in their mind, the reward is getting in. WPI on the other hand started prepping him with support to apply for a Fulbright, a post graduate fellowship, before he’d even signed an acceptance letter. It was their way of showing their support to entice him to choose them. $80k didn’t hurt either.
From IL, not wanting to be in an urban environment, I would certainly look at Missouri S&T. My sister went there and she was accepted to MIT. With COVID, I don’t know if they’re doing it, but Jackling is worth consideration for the summer whether he applies or not.
My niece (that sister’s daughter) goes to Purdue and likes it. Her main complaint is that it is isolated. Not like Rolla isn’t though. Ha!
I’d also add Michigan Tech and Iowa State to the mix.
https://futurestudents.mst.edu/summer-camps/jackling-introduction-to-engineering/