I found this to be a great program. It really teaches kids to think about the story rather than just hear it and be done. We started it with ds in 7th grade, so I had him watch the DVDs with me. We also used the lesson plans which I downloaded (I think you have to buy these separate now) - they use O. Henry short stories for practice. This worked wonderfully for us.
For a first grader, you would probably just watch the DVDs on your own and then teach it to your children. The O. Henry lessons may be a bit beyond them too?
After that you may be ready to continue on your own using their socratic list (questions to ask the student). If you want more guidance, the Center for Lit (Adam and Missy Andrews) also has other resources to use after TTC. There are 3 levels of Ready Readers that use their method. I would think the stories in the first book would be great for your 2 older daughters. Here is a link where you can see samples: http://www.centerforlit.com/Materials/RR.aspx
I actually used this with ds 8th grade, and though the stories were definitely for much younger children, the analysis helped me feel more comfortable continuing the method on our own using our own books.
Hth,
Kathy