Thanks for all of your reassurance. Here is what I ended up sending:
Hello again. After much careful thought, I have decided that this project is not something I am able to take on at this time. I am simply unsure on my ability to deliver this project as I would want to, the best that I can. Thank you so much for your consideration, and I wish I had someone to refer you to to complete this commission; None of my art acquaintances are taking commissions at this time, unfortunately. Again, thank you and I wish you the best of luck in completing your project.
Namaste