I used to use a mix of gizzards and hearts, but the gizzards seemed too big so I would cut them in half or thirds. I got tired of the extra knife work, so switched to just hearts, which seemed the perfect size as-is, and Missy didn't mind the change.
I've always been worried about the bone meal, since calcium is critical for dogs and I don't think Missy would get enough without it. But, definitely go with your vet's recommendation.
I was wondering, have you tried doing a Google search for dog food recipes? There are a lot of sites out there that have some, although you have to be a bit careful. Many of the sites seem to me to be biased against food that is perceived to be bad for people, like eggs. But, they may give you more ideas on what you can try.
She recommended a book Dr. Khalsa's Natural Dog; A Holistic Guide for Healthier Dogs which has lots of great info and recipes. Unfortunately, Gypsy will only eat 'em rarely, if at all. I finally understand the expression "stiff-necked", 'cause it fits Miss Gyps to a tee!