I did a study abroad to China through Project Go this past summer, and I can assure you it is definitely not an opportunity your DS would want to miss. First of all, you are sort of right, a study abroad is basically a glorified vacation, but as someone who has been through it I can assure you that it isn't a negative thing. I not only took classes in Chinese, but also traveled throughout China seeing first hand how life is there, and of course practicing what I learned in class in a real world setting.
Sure a study abroad class may not be as "rigorous" as a normal class, but if you put more effort in you get more out of it. Language courses aren't like math courses, where you just memorize a formula and you know it, you have to go out and practice constantly to improve your speech and what better way is there than being able to speak to actual native speakers on a 24/7 basis. Also you not only learn the language but the culture behind the language as well.
I really can't say enough good things about doing study abroads in general, but seriously Project GO pays for a majority, if not in full, for the trip, and your DS has little to no obligation afterwards (I just had to take a test afterwards to see if my language skills improved). Not to mention your DS will be learning the culture and language of a country that the US government deems critically important. This is definitely an opportunity every ROTC cadet should take.
If anyone has any questions feel free to PM me or continue posting here.