Your kid sounds great.
I don’t think he needs to limit himself to civil engineering though. There are people who work in the area he’s interested in with degrees in Agronomy, Forestry/Natural Resources Management, Geology and even plain vanilla chemistry. Organizations like Doctors without Border and other global relief efforts need lots of different skills. So if your son has looked at the curriculum of a few Civil Engineering programs and think the courses look interesting- fantastic. But it will be hard to combine language fluency AND the ABET curriculum (agree that playing a sport on top of that will be tough- not impossible but tough). So another adjacent type degree is likely to give him more flexibility with course sequencing.
Spouse has a degree in Civil Engineering (and a BA in an entirely different, unrelated discipline) and had exactly one “Gen Ed” type class in four years. So you aren’t looking for a double major in order to gain language fluency- but he’ll likely come close to filling up his “free time” with those required classes.
Good luck.