Screenwriting : Pass or play by Heather McCluskey

Hey guys, I have a lot on my plate at the moment and I've just been asked to help co-write a based on a true story motivational script derived from a children's book the client wrote. My genre is sci Fi /fantasy/adventure. Not saying that I can't write other genres, I've done true stories in the past, but I find it painful to write and very time consuming, especially partnering on a project with someone who is inexperienced and only wants to work on it a couple of hours a every two weeks and is "in it for the long haul." I'm used to knocking out 1 script per month and this seems like i may lose momentum and passion for the work stretching it out over such a long period. Though I don't want to turn down work I am willing to advise that I may not be the best person for the job. I know I could write it, but at this point in time I already have a lot of balls in the air. So I'm asking are there any of you out there who love this genre?  Anyone I can refer? What are your thoughts on the subject? Pass or play?It would be turning a children's motivational book into a screenplay, co-written with the author of the book who the story is actually based off of.