Latin would be the best language for a first foreign language...the kids would have to learn grammar, and would improve their English vocabulary immensely. Plus, learning Spanish, Italian, French, Portuguese, Catalan, or Romanian later would be much easier.
BINGO! This man knows his stuff. Once you know Latin nearly every European language becomes easier. That's why many of the Popes could speak fluently in ten, twelve or more languages. They learned Latin first.