Dazey - I'm tired just reading this - applause to you for what you are taking on!
I wonder if the class by the archaeologist could lead to other classes in other subjects? Is it time to hire a tutor in one or two areas?
What about online writing classes - I've heard great things about
http://www.onlineg3.com/Are there any local homeschool resources you could tap into?
Would the library have a book club?
CTY online classes?
Just some thoughts...
Can you set up DS9 to coach DS6? or the 3 year old?
What about a unit on 'Home Economics' so that they are very active in running the home?
Housefairy.org?
