Honestly, from where I'm sat, I'd point him toward an online MS in Data Analytics rather than something heavily CS-focused. If he already knows his interest leans towards analytics, stats, and ML over hardcore software engineering, there's little point forcing a pure CS route. Better to build depth where the interest already lives.
The couple of years at Amex counts for a lot. That kind of hands-on analytics experience often outweighs stacking degrees without real-world backing. The master's will work best if it helps him move into stronger DS, analytics, or product-focused roles - not as a generic credential.
I've seen online MSDA/MSDS programmes deliver real value for people who already have relevant experience and want to push into higher-paying analytics and DS roles. But I wouldn't choose based on school name alone. Look at the curriculum, industry connections, and flexibility first. Also wouldn't stress about his civil engineering background - at this point, his work experience matters far more than undergrad.
If you want, happy to point you toward a comparison of online MSDA vs MSDS programmes - a lot of them look the same on paper but differ quite a bit in practice.