My oldest son is like you describe your daughters to be. He whines and hates to do school work of any sort. He was not this way in ps...which leads me to believe he is seeing how much he can get away with since we have changed it up on him all of a sudden. We too are using Calvert, but I find that I don't stick 100% with what the lesson manual says. There is nothing wrong with shortening assignments, allowing them to type instead of write, even occasionally letting them dictate and you write for them. Not that you want it to become a habit, but my son struggles with penmanship as well as spelling, so for him, if I let him dictate and I write, he takes off! He is so creative. But, if he has to do it on paper himself, he does it the most simple, least creative way he can think of just to get it done. For me, I had to discover what I wanted. Do I want penmanship and spelling right now, or do I want him to enjoy writing and being creative and the rest will come as we go forward. I chose the latter.
I think this generation and all of the stuff kids see on TV, all the stuff they have at their disposal (TV, DS, Wii, Pokemon, Transformers, etc), they have forgotten how to go outside and shoot hoops till dark, or read a good book for entertainment.
This is going to seem drastic, but we turned off out TV. Completely. We disconnected the cable. It is not there and he cannot watch it. It has been a struggle, but over the course of the summer, it has grown on the kids and they are finding more and more things they like to do that do not involve sitting on the couch for hours watching mindless nothing.