I know we all run into that question and it varies depending on the children, what you want to accomplish and what your goals are, but it's still something that on occasion needs to be addressed. Do we go from 8 am to 3pm and only have lunch, "recess" etc? or do you do the complete opposite? Radical unschooling? No limits at all? or do you do a hybrid system?
I can only tell you what I do and that's because for us it works. Now what I do may not work forever, it may not work for your family, it might work for ONE of your children but not the other. I'm not what I consider a complete "unschooler" we do child led interest learning. It helps that my kids are interested in pretty much everything. I make sure that what ever I do in a unit study has all the subjects incorporated. For example: let's put together a unit study! Pick a subject, any subject.....
Okay. Let's put together a short unit study on Sharks! This should be fun!
Sharks are found in the ocean (and yes, some rivers, those darn bull sharks!) how many different oceans are there? which ocean is closest to where we live? spend some time looking at the globe or world map finding the oceans, they countries that are near each one, etc. work on North/South/East/West. Etc.
What is the smallest shark? What is the largest shark? what is the size difference between them? How much bigger or smaller are they compared to you (the child)? How fast can they swim (pick three or four species) which one is fastest? which one is slowest? How fast can you run? are you faster or slower than each species? How much faster or slower?
Find a few age appropriate books and read them (or if the kids can read them on their own great), have them write what they liked about the book (or didn't like). Discuss the book together. Ask them to tell you what happened in the book. etc. who the characters where, what was the plot, etc.
How about a Mega shark teeth science kit? or a shark anatomy kit? How about a robotic shark? Shark casting kit? TONS of fun stuff to do!!
You can do a few things here as well. Social life of Sharks? what about societies views on sharks (pick a few different geographic area's to get a good look at how other countries/cultures view sharks). Discuss. Ways to live with sharks. Why would sharks going extinct be bad?
It's really that easy. Yes it can be time consuming for you to get all the stuff together, but their enthusiasm for the subject and how fast they learn is great to see! Of course, it can be as detailed as you want them to get (older/younger student) you can add in a field trip to a local (or semi-local) aquarium. Watch a shark documentary together. See what shark research is going on.
You might do a half hour a day or a full hour depending on the kids (and if they are really into it, you'd be surprised at the amount of work they can accomplish!) You might do it in addition to some of the other stuff you do on a normal basis. Educational games, some worksheets, etc. you can do one or two unit studies (depending on how many kids you have, if they do/don't want to learn about the same stuff etc.) Kaitlyn and Arianna have some mutual interests and then have some of their very own.