So many tightropes to walk.
To get the absolute best need-based aid (esp. the schools that don’t consider home equity), you have to go uber-competitive. And with the URM-bump, your son may well have a shot at uber-competitive, if he can get his math scores up which is likely quite realistic with some focused prep. (Plus, the most competitive schools are able to be more successful at recruiting a diverse student body than schools that are still excellent but one prestige-tier down.) But, if he scores an uber-competitive admit, there may be a higher risk of getting pushed out of engineering by the steep learning/grading curves in a highly demanding program with an exceedingly well-prepared peer group.
Diversity-wise… there’s a trade-off in terms of URM advantage - the schools that will want him the most badly are of course the schools that struggle to recruit a more diverse student body, and it sounds as if there’s only so far he wants to go in terms of being one of the few tasked with providing the diversity, in return for an admissions/scholarship advantage. Plus, as a Black+Hispanic student, even some diverse-on-paper environments may not be as good a fit as they might seem, depending on how he identifies racially and culturally. My “surrogate kid” who is living with me is Puerto Rican and is attending a highly diverse community college near my home. The most common question he gets is, “What ARE you?” The Hispanic students, who are predominantly Mexican-American, parse him as black and are shocked to discover that he’s a native Spanish-speaker. The black students don’t parse him as black at all, and the professor in his African-American History class even argued with him when he referred to himself as African-American in class. At times he has ended up feeling more excluded than he has in majority-white environments in the past! However, a hypothetical student of similar appearance, with one non-Hispanic African-American parent and one Mexican-American parent, might have quite a different experience in the same environment. This what was in my mind when I suggested UMiami, where one might find a greater black/Hispanic overlap because of the large population from Spanish-speaking Caribbean countries/territories. Plus, there are a fair number of students who take the articulation pathway from Miami-Dade, one of the largest community colleges in the country, so he might have better luck there with his community college credits than at other similarly-elite private U’s that don’t take as many CC transfers. But… the question of where he would feel most at home, diversity-wise, is a very individual one. I can’t imagine my “surrogate kid” fitting in at NC A&T, even though in theory he would love to transfer to an HCBU; but he’s never set foot in NC or any other southern state - it might be ideal for your son who likely has a completely different set of cultural competencies! All of which is a very long-winded way of saying that “diversity” numbers don’t tell the whole story about any given environment; he will need to think about what he’s looking for in terms of community.
The other balancing act is re: how much transfer-credit to seek. On the one hand, you don’t want all that college coursework to go to waste, but on the other hand, trying to place too far ahead will limit what programs are available to him, and perhaps deprive him of some really wonderful educational experiences in terms of lower-division coursework that is different, qualitatively and depth-wise, from what he has gotten in his DE classes. You and he will have to decide where the “sweet spot” lies in that regard. (And of course that question dovetails with the funding issue - spending more time on lower-division classes would be a lot more palatable with full ride than if you’re paying/incurring debt!)
Is he considering applying through Questbridge? He appears to meet the criteria, and the funding would be excellent if he were to “match.”