Well, experience tutoring kids this young is a lot to ask when you also want the ability to teach advanced mathematics... A friend of mine in a similar situation near another good university employs a good undergraduate and that seems to be working - worth a try? Backed up with good material, so you're not asking for curriculum design, just mentoring and explanation as needed.

For the material I strongly recommend Art of Problem Solving - much deeper than what I've seen of Khan.

Email: my username, followed by 2, at google's mail