UT Austin is a reach for Business and Engineering. Unless your income falls under the new tuition program, I doubt your family will get any money.
Your DS might be admitted to A&M or to one of the other avenues to engineering like Galveston. Can you afford A&M?
You should take him to visit UT Dallas where your DS will receive merit money (the NMF scholarship is excellent). UTD is strong in both engineering and business. The University of Houston is worth considering for engineering. Make sure Texas State and UNT have ABET accreditation for engineering degrees. I think your DS will receive money from TCU but TCU might still too much so run the NPC for TCU. Note TCU does NOT have engineering. Try the NPC for SMU and for Trinity.
Start investigating NMF scholarships. Check out ASU, Central Florida, Florida State, UNT and UT Dallas among others. You will have to search college websites for this info.