not sure how you would use a band saw to do this as there's no way you're going to finagle a 1/2" deep blade around a BXA holder slot.
You'll be fine with a carbide endmill. Start slow, keep your eye on the chips and ear on the sound and take it easy. Step down to cut the first slot, then step over (side milling) to widen it to width. Even if they're through hardened, it's not to super high levels, most say maybe 50RC if that, so carbide will be ok, HSS I'm not so sure. Run it slow with lots of oil and hope for the best!