Our church does 7-8 fish fries a year, cooking 150-220 pounds of fillet each time. We get our oil from a local butcher shop, it's labeled liquid shortening, basically liquid lard. It comes in a 5 container for around $30-$35. Alot cheaper than peanut oil and we don't have to worry about any allergic reactions.
As far as reusing oil, you can put a peeled irish potato in the oil after cooking and let it fry for awhile, it will help absorb most of the impurities. We don't do it at the church, but I've done it for my turkey frying oil at home.