Ah, this old myth is still around Dogs in the racing kennels get a mixture of raw meat (ground beef, usually) and kibble everyday. People eat things that have different digestion rates all the time. It really doesn't make any difference, you can combine kibble and raw if you want, I do it every day for the girls. If you want to feed the two thing seperately, that's fine too, but you don't have to.
Also, for the OP, the white tripe you see at the grocery won't hurt your dogs, but it has little nutritional value, so don't feed it as a meal, rather as a treat. The stinky green tripe is what is very, very good for them The fresh pigs' ears should be ok, but I would take it slow, just because you said the pig's heart gave them the runs.