I was hosted by an american family for one year. I was 16 and would go to school, it wasn't voluntary work, but apart from that it should be quite similar. I must say I did suffer from solitude from time to time, but as I said I was very young, I couldn't drive (so, that being America, I couldn't go anywhere without being accompanied), and my SA was a bit worse than it is now.
Still, it was an extremely interesting and enriching experience, plus I learned english, which now allows me, among other things, to browse over "social phobia world"
Besides, I'm sure working togheter with your hosts, as I suppose you will, will help you overcome the initial impact of having to socialize with strangers.
I wish you the best of luck