Hi K.,
I have been thinking about the same thing for the past several weeks. I am so glad you posted this because we've also been searching for classes that teach Mandarin at my child's age (2) and I was able to find out about Lango.
About your question, I heard good things about the spanish school house, plus their prices aren't too steep. But I have been thinking of getting a playgroup together myself and just doing some simple teaching to the kids of this age group. What i have done so far is getting the books from the library (spanish/english books for toddlers) and started teaching my little one. He knows all of his colors, shapes, and up to 15 in spanish. He also knows many of the animals in spanish and a couple of phrases as well. I started off doing Mandarin with him but then he would only want to speak mandarin and so I had dropped it and never picked it up again. And since his school has a spanish class (not really) I decided to pick up teaching him spanish.
The books from the library are great and it works well for children of this age group. Also the Jumpstart Spanish CD ROM for preschoolers is pretty good. My son has been using the computer since age 1 and doesn't need me to load anything. He jumps on the computer, logs in, starts his game and plays it. So if your little one knows how to maneuver around the computer and can use the mouse and keyboard interchangeably, then this would be a great option too but if you have time to sit with him/her you can both do it together. I think the CD is very well put together and is a lot of fun!
Hope this helps!