I have Duolingo as well. It's free and interactive. If not for me having a business that requires 24/7 of my time, I would benefit much more from it. But I do log in and do the lessoms when I can. I do recommend it because it is immersion amd your can do it at your own pace.
Most of the timeI take a more passive approach.
I listen to Latin music all day, and do a translation of the lyrics through Bing Translate. It doesn't take the place of concentrated study, but I hear the language while I'm working and I can easily get a translation. It's not conversational, but the music stays with me and I even dream of the lyrics. So it kind of gets into my subconscious.
Your son being a teenager, could learn a lot from listening to the language, beat and pulse of the music (IMHO). I won't take the place of fornal studies, but I think it will get him in the groove and give him a better appreciation for Latin culture. Music is the univerxal language and it defines Latin culture.
That being said, I do find myself interjecting Spanish words and phrases on a daily basis, often without me realizing it Not because I study them, but because I hear them and have them somehow integrated into my brain.
I guess I really need to just set aside an hour a day to Spanish studies, just like I set an hour to Zumba.