Congratulations on realizing how important a species-appropriate diet is for your little carnivores! It's awesome that you're willing to make this effort for your new kittens.
Some of the answers to your questions are going to depend on what raw-feeding methodology you use. There are three: Grinding, Frankenprey and Whole Prey.
There are a HUGE number of ground "recipes" out there, here are two sites to check out: Cat Info
and Cat Nutrition
. Supplements are generally accepted as a requirement for this feeding method.
Frankenprey feeders use the 80%, 10%, 5%, 5% guideline:
80% - 87% meat, fat, skin, sinew, connective tissue, heart and gizzards
5% - 10% edible bone
3% - 5% liver
5% other secreting organ (kidney, spleen, brain, testicles, eyes, etc.)
The only supplement usually needed here are Omega-3s, unless you're able to procure grass-fed beef and poultry products. Salmon oil caps are typically used, but a Sardine a week is sometimes substituted (I feed sardines).
Finally, of course, you have the Whole Prey method, which is exactly what it sounds like - whole mice, rats, guinea pigs, chicks, etc. are fed. No supplementation is needed with this diet, since you're giving your cat exactly what he evolved to eat.
This is a very, very general overview. Which method most resembles what you've got in mind for your cats?
This is Cat Forum's Natural Diet Resources
thread, which you might find helpful.
My catforum real-time transition thread is here Taking the Plunge
There are a ton of helpful people on this board, so you're in good hands here!