DC is humid, but if one avoids taking classes during summer sessions it could be an option.
The Faculty of Languages and Linguistics is a gem within the College. Your son could choose from a number of options after his first year there. He could double major in Arabic and Economics whilst minoring in Applied Mathematics or Turkish. Or he could decide to double major in math and economics with a language minor.
Alternatively, he could pursue a dual degree between the College and the McDonough School of Business through the newly offered International Business, Language and Culture major with language concentration of his choice.