My DS6's working memory tests even higher than his VCI on the WISC, and I'm pretty sure that's because he memorizes things as a coping mechanism. Wouldn't the guided reading activities just encourage more memorization? Is that what you're going for with these sorts of activities, or is there some other mechanism at work there?
I had the same concern when we started. My DD can memorize large passages with great ease -- this is how she fooled her kindergarten teacher into thinking that she could read. With guided reading, I found that when she tried to do it just from memory she made subtle mistakes that let me know that she wasn't reading word for word. I then tell her to go back and reread the sentence. I let her know that she missed/added a word/ending. Also, as we have done longer chapters, she can't keep it all in her head. She really has to practice reading the words on the page and not faking it.
As for the recorded books, we also tried this but my dd didn't like it. Maybe she likes the one-on-one time that comes with guided reading.
