Your Business Math Question

My nine year old is finishing up MUS Epsilon and thought he is anxious to start Zeta, I am thinking I’ll hold off on that until September and have him use the Pet Store version of Your Business Math for the rest of this year, letting it run in to the summer if need be, though things don’t tend to get done around here much in the summer when the weather is just too nice to be cooped up — especially after such a long winter as we’ve had this year.  Would I be pushing it too much to have him finish the whole thing in 2-3 months if he were to do it daily?  

I am also thinking of having my 13 year old do it, too, in hopes that he’ll realize math really is something he needs to know.  He has been talking about owning a hunting store when he is an adult, so this may give him a better picture as to why he needs to know this stuff.  He is currently doing Life of Fred, but I am not finding it is a good a fit as I had hoped.  I really am at a loss as to what to do with him next year — moving him back to MUS means he is a year behind his much younger brother, a real blow to his self-esteem which is why I switched him to LOF in the first place.  He’s only on the second set of Bidges for Fractions and has been through every one without passing. We have been on a break this past week and I have been trying to sort it out how to help him using the curriculums we have on hand because I really can’t afford to buy two expensive math curriculums.