My two are just gannets and don't turn their noses up at anything
They eat raw kidney and liver (of any kind - well, chicken, pork and lamb are the ones they've tried
) no probs, although admittedly it's always mixed in with tripe so it could be they're too busy hoovering the tripe up to notice...
I'd try flash frying though, cooked liver smells alot better than raw to me