That is a hard one. I find that I struggle with the additional problem of wanting more convenience foods and all sorts of similar coping mechanisms that cost too much when the more people don't appreciate the effort of my cooking, or even just if I am having extra stress. I'll pray for you. I understand in a big way how badly that would effect me.
With 8 and 5 year olds you might be able to expand what the kids will eat even if you can't do much about mil. Its a long slow process. But I have a few suggestions about it. Do you ever watch food tv? Is it an option for you? I don't know what the shows are right now since we don't have cable or satelite anymore and strangely I don't know how to even get onto pbs with the computer/tv set up my DH has going. But if you can find a cooking show that you like that uses mostly real food rather than processed convenience foods, you might be able to end up with the kids sharing it with you once in a blue moon. Because I really enjoy cooking, cookbooks and cooking shows my kids naturally
got into those things a little too. And it can make a huge difference.
Some people get similar results sharing gardening with their kids.
The nicest added benefit in my opinion is that in the long run you can end up with a family full of cooks. I've always loved to be able to say to people that every person in our house cooks. And now that my children are older the
amount of cooking they can do is a huge help. But the fact that they aren't picky anymore is great too! It just isn't the most obvious of concerns anymore since it has been so long since I've had to deal with it with the older two. lol.