If you can, set up morning 'sessions' of 2 to 3 hours and split between maths (what they're currently covering at school), English (any writing/vocab/basic punctuation and grammar/comprehension etc. exercises) and occasional atlas/map work for geography. You can devise some 'find the place' games with directions and pointers. Maybe a bit of history if you have age suitable resources. Basic science should be added if poss.
I'm long retired, and used to make up much of my own material, but as said above, on-line stuff is abundant now. Bit of reading after lunch and that's the school day !