Dear Marlaina,
Rather than looking at the direction the retaining wall runs or the trees are locate. First look at the house from a space feng shui perspective: Which direction does the house face, to which side of the front door is the larger tree, etc. Remember, you can always call into Learning Strategies and ask to talk to a Feng Shui coach. S/he isn't going to do a full on consultation on your house, but can clarify somethings where aback and forth works better than a chopped up email or post conversation.
Shawn
