Great minds must think alike- Thats how my wife got interested in photography,, I had her start coloring my prints. She uses acrylics, pencils, as well as oils. Freestyle, and Porters, both have coloring sets, also instructions on the subject.
Rick
Those pencils should work fine. A light touch is needed - you can always add more, but you can't easily remove it once it's there. A lighter touch makes it easier to avoid lines and scratches. Matte finish paper is easier (even RC works, as long as it's matte).
You may have to experiment a bit to find a paper and surface that takes the pencil in a way you like, but it should work fine. Prismacolor pencils have been around for a long time and have a great reputation.
I was talking with a monoprint maker the other day, and in the conversation we agreed that photographic paper (and prints) would make great plates for monoprints using water soluble media.