Cayenne pepper tends to be spicy on the end/aftertaste. I've had a cocoa made with vanilla, saigon cinnomon and cayenne. It was very sweet, the cayenne wasn't noticable until after you swallowed. It was excellent.
Home depot buckets aren't NSF. But I wouldn't worry about it too much. If you are concerned about it you can buy 22 qt cambro containers at any restaurant supply store. For around $10-$15 each.