I just Googled the Thomas Kinkade sets you are talking about an they have a number
overlay, which means you set a transparent film on top of the inked drawing, and that has the numbers on it, so the numbers don't show up in the final picture. I think you do see the inked in lines though.
Colored pencils are not opaque. They are translucent, so you do see through them. Perhaps you are really interested in pastel crayons as they would provide a much thicker coverage and are opaque. (I don't work with pastels, so I don't know anything about them.) Oils, acrylics and pastels are opaque.
But, since you want to be using the pencils to create your own quilt designs, why wouidn't you just draw in the lines with the same color color pencil?
Here is a link for how to use colored pencils:
http://books.google.com/books?id=bYO_v1KVNM4C&pg=PA12&lpg
On the left side, at the top, under the word Required, is a button with a + sign, in which you can enlarge the print size quite a bit, so you can read it better.
The Prismacolors do break easily as I recall. I haven't used colored pencils in years. But the different brands have different hardness & softnesses to their colored pencils and they produce different results. If you are making squiggly lines, you might want a nice, hard, sharp line. The creamy pencils would be great for the background colors or to fill in without a lot of lines showing.
If you can, it might be better to get an assortment of different brands, until you find the one(s) that you prefer. In the better art supply stores, (not craft stores like Michael's,) they actually put out little pads of paper so artists can try out the different pencils, ink pens, markers, etc., before buying. One of the perks of a real art supply store.
ETA: Here's a page on using oil pastels. It even talks about using a Q-Tip and vegetable oil to softly blend colors together. You can use a white over a darker color, etc.
http://books.google.com/books?id=z5kcr4xhV70C&pg=PA46&dq=No+Experience+Required!
This page talks about how
oil pastels are much safer than the dusty, chalk pastels as they are dust-free. This book is written by the grandson of the famous oil painting company: Sennelier,so he would know what he's talking about. He says using oil pastels are akin to drawing with lipstick!
http://books.google.com/books?id=nFUAv8XehKcC&pg=PA8&dq=oil+pastels