So, I saw three questions in your post. To the first, how does a partial raw diet affect a cat, I'd say - every bite of healthy food is a bite of healthy food.
If the raw food becomes three quarters or more of your kitty's diet, however (and this would be a good thing) you might want to start tweaking it to ensure he receives an appropriate balance of meat/bone/liver/organ (usually defined as the 80/10/5/5 rule).
To the second - dry food does take longer to process than raw, so feed them as far apart as possible. I understand your desire to keep things normal for your older kitties, but if you can, gently and without upsetting anyone, I'd ditch the dry altogether... it's just such an unhealthy "food" product.
And to your third question - I think the reason your cat eats around the bone is most likely because the bones you seem to feed are sized for the dogs and are, therefore, too big for the cat to break. He's come to realize this and now doesn't even try.
Start offering him very small bones, like quail ribs. Leave some meat on it and coat it with something he really likes to tempt him. After he's successful eating it once, he's likely to be more willing to try again.
- - - -
StormChaser, I feed only the wing tips and the middle pieces of chicken wings, and I cut the middle pieces in half between the two bones, not across them - and I leave all the meat on. I save the largest part of the wing for my own plate (barbecue wings, mmmmm).
I don't offer bones any bigger than chicken wings.