Sorry I'm late with my "say" on this one
. Chicken frames, turkey necks are my fave "bone meals". Older dogs can be a little more sensitive to skin and fat (which can cause the squirts) so keep that in mind
and I agree with Eli with the liver - I would not feed it every day.
As for the heart, I hope I don't confuse you with this but here goes.....heart is an organ so it is offal BUT it is a muscle as is stomach so it can be fed as a muscle (meat) it isn't nearly as rich as say liver or kidney
- make sense?