I had my son do Home2Teach writing classes for about a year. When classes were in session, it meant an hour a week at the computer with an online typed lesson, then things that had to be done daily. I think they are about $75 a session, 3 per year. Might not fit your budget right now.
How about You Tube schooling for some subjects like science and history. Depending on the age of your kids, you can have them watch NOVA, American Experience, Secrets of the Dead (that kind of combines the two) or pick some topic (Castles, middle ages weapons, etc) have them watch it and then write something or discuss it with you. There are all sorts of people that do shorts of various topics, P D Grey, Veritasium, all sorts....have them watch those. Reading: either audio books during lunch or travel places or reading things that you really enjoyed when you were a kid. When Grandma arrives, it would be really cool if the kids could spend time learning about (and writing down) stuff about her life, stories about her family, going through old photos and things like that. All of that can REALLY bring history to life.
Moby Max is supposed to do up to 8th grade. It might now have social studies, not sure. Started as reading and math, vocabulary, writing if you wanted to pay extra. It is largely free, except the writing.
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