I would let the 10 yo work alone in language arts and math, but group him with the others for science, history, bible, latin etc. adjusting the work level for each child. Have you looked at TOG for your crew? You could keep all of them on the same page that way.
My 5th grader is doing the following:
Abeka math 5
Rod & Staff Science 5
Rod & Staff English 5
Rod & Staff Spelling 5
IEW Ancient History Based Writing Lessons
TOG Year 1
Mind Benders
Latin in The Christian Trivium I