For the shadows - I'd make a few renders... one would be of the house and ground one would be of the trees and ground (to get shadows on ground and trees) one would be of the trees near the house and the bit of the house that has shadows on it (to get the shadows on the house) Then merge all the images in a painting program later and you'll have all the things rendered with shadows in the right places (I think).

Dreams are just nightmares on prozac...
Digital WasteLanD