Did your son know Spanish before starting the program? Our DD didn't and we found her instantly challenged when she stepped into the classroom. This really set the stage. Before moving her into this program we tried a social preschool but found out quickly that it wasn't a good fit. DD was just not herself and everything was for older kids: writing, drawing, reading, math, etc. We learned we have to keep her challenged and when we do her mood and attitude is great.
The school starts French with the 4 year old class but it is really more of an introduction since they get 1 hour a week. The Mandarin was added this year and I'm super excited about it because I planned to start her in Mandarin in another few years as an extra activity. My DH works with the Asian market within his job and I see more and more companies doing so. I just think it is an important language to acquire. I have a few friends who have adopted children from China and I know there is a Chinese center in town that offers Saturday classes. It might be worth looking into in your area if you think your son would be interested.
