
The best bones to introduce as part of the raw diet are actually chicken or turkey bones, not only are they soft enough for them to easily chew, but they are actually one of the best nutritionally. Lamb bones are a second best, they are also very good, lack in omega 3, and can cause a loose tum as they're a little bit richer than chicken/turkey. Chicken and turkey bones are quite soft anyway, and lamb bones being from a young animal, are also quite soft and easily manageable.
I personally don't give marrow bones or the weight bearing bones of large animals, as these can be prone to splintering, I know of someone who recently nearly lost their bitch after leaving them with a marrow bone as a treat. A large piece splintered off and wedged in the oesophagus, nearly killing her.
If you think your dog might swallow bones without chewing, the best thing to do is either hold on to one end, and/or bash them up with a rolling pin, meat hammer or similar, so there aren't any large pieces that may cause a problem.