(posting for the first time on this board)
just thought i'd add, i've found doing a "unit study" on a particular math topic/concept is very popular with my DD when i run out of math curriculum for her. we've used some of the free downloadable lesson plans from the Core Knowledge Foundation that are written for classroom use and adapted them easily to homeschool unit studies to explore things like time, money, fractions, algebraic thinking, measurement, etc. and sort of beef up our Singapore/Miquon work here and there.
ITA with everyone else- let him take it and run with it.