This is hardly the strongest argument against changing the definition of 'Planet,' and increasing or decreasing the number of said objects. Having just looked through some of my GCSE textbooks from 2003 I notice that on the section of the planet Saturn, its moons for example are simply asserted as being 46+. This avoids confusion and accepts there may be more. This is probably what will happen to the number of planetary bodies. Placing an addition symbol negates the argument of textbook cost.
Just a thought.

CJ