Latin will give you the structure and basis for all of Europe's romantic languages, Spanish, Portuguese, French, Italian, Romanian, and Catalan, Corsican, Lombard, Occitan, Gascon, Aromanian, Sardinian, Sicilian, Venetian, Galician, Neapolitan and Friulian amongst others.
Or just not bother and let him sort it out himself when he cares. A friend's son is Dutch/Chinese and has learned to speak Dutch/English/Cantonese without having to allocate specific adults/rooms or times of day to any partiucular language or dialect.