To not plagiarise instructional material?

Well your best bet is not to use it if you cant give credit to who the information belongs to because as you know that's a serious offense.

What a simple solution. Do you mean, if I dont know were I got it from. then dont use it.

I could just laugh at my self sometimes the way I can over think something.
Thankyouj brbj

It's an interesting question, and one that comes up a lot in education. Teachers joke that, although they all advise students against plagiarism, the profession is full of the worst perpetrators. The reason that classroom teachers (and homeschooling parents) get away with it is because they're not making money off of the stuff they create (e.g., they're not selling it). What you're contemplating doing is taking other people's ideas, putting them together into a book, and selling it. It seems like you're willing to admit, "I didn't create this stuff, I just found it, but try it because it works." This is a noble gesture, but it doesn't stop your book from being a work of plagiarism.

It appears that the problem you are facing is that you lack the academic credentials (and citation experience) of someone with a Ph.D. in education. That is, most books written on teaching strategies are published by professionals, and the books are full of citations linking each strategy to a research study that proved such-and-such worked. Your problem? You did these things at home, with your own kids. There was no peer review, no control group, etc. As such, you are free to write a book full of things that you did with your kids that worked. For example,"We read a story every night before bed." No one holds a copyright on reading aloud with their kids. See what I mean?

The trouble comes when you start writing out specific strategies or lesson plans that you got from somewhere else. With education, it's extra tricky, because with almost 3,000,000 K-12 teachers currently working in the U.S. alone, chances are that at least one of them is doing or already did pretty much the same lesson plan. The "potato batteries" you mention are common in classrooms. I have no clue who first performed this experiment, but my best guess is that it was at least a century ago, in the earliest years of the study of electrical currents. So, theoretically, there's no source to cite provided that you use your own words and illustrations.

Your biggest stumbling block comes from your own phrasing: "I've included many of my own words..." Just "many"? It comes across like the bulk of your book involves you presenting items/ideas that you are pretty much copying from someone else, although you can't remember the source. This is where you can get yourself into trouble. Without even realizing it, you could end up incorporating half a dozen lesson plans from a book you read ten years ago. If the author of that old book finds your book and sees you've "stolen" his/her lesson plans, you could get sued.

A way to avoid plagiarism, as well as (perhaps) create a more interesting book, might be to focus more on how you personally tweaked popular plans to fit your daughters' needs. For example, "Potato batteries are a popular science experiment for kids. They work like this...YADA YADA YADA... My daughter had so much fun with it that we tried the experiment with other food around the house, and this happened...YADA YADA YADA." In other words, make it personal.

Remember that the people who are going to read your book are people like you--they are homeschoolers searching for gems and pitching the rest. If you're simply looking to say "try this..." you're better off writing a blog that links to stuff online, or that cites other books (which you can write about as you read them).