Is your concern that he already knows too much of the 7th-8th curriculum to make that feasible?
For whatever it is worth, the pacing sounds far better in a compacted course like that-- maybe even better than "higher level" math. If your school's accelerated mathematics options include this kind of compacting in coursework, that's a great thing. Well, I suppose not if he's ready for Algebra and this is being suggested instead. Seeing material you mostly know at a faster pace only makes it slightly more bearable.
I'd let him show them what he can do with Khan, myself. They'll probably believe that a lot more than anything you bring to them at this point.
