Are you using ECC? If so, which parts do you really hate and are there any parts you love? You could just use the guide as a...well, guide, LOL. Learn a few things about each country and cook something from that country. If you are not the type who likes to wing it, you'd just have to scrap the whole thing.
I purchased ECC in the 09 school year. I was using it w/ a 3rd grader, 6th grader and 8th grader. We didn't last more than 10 weeks. But, there were certain things I kept saying I liked about it. I really wanted to use it with just one child but I needed to sell it so I could buy stuff for my other kids.
Guess what: this year I bought the whole thing again.
But this year I'm using it with one child...my 5th grader. I feel better about it this year.
So you could loosely follow it and veer off and do your own thing when you find something interesting or, if you have the cash, buy all new stuff.
To be honest, I don't think there's anything at all wrong with just using library books and the internet for science and history.