My first question would be, does DS think this is the best he can do? If this answer is no then he should look into taking it again. 34 English is awesome and 29 math is a good score (about a 670-680 SAT) and is slightly above the average USMMA.
Remember that admissions to any of the SA's that require a congressional nomination start out as a local competition. You have no way of knowing who your competition is so it is important to control what you can control and put together the best package you can. SAT and ACT scores are only a piece of the puzzle but they are a rather large piece.
All this being said, USMMA is a STEM-oriented school and a higher math score will make him more competitive. Khan Academy has good SAT and ACT prep courses that may help him raise that 29 to a 30+.
I agree with @HCopter, I would sign up for Math again.