Hey, who said you had to have kids to own a dart gun.Great idea, you just need kids of the right age !
I usually use an old magnetic cup-hook. The magnetic base is about the same diameter as the the buckets.
Takes a litle twisting to break the oil film, and occasionally the film proves stronger than the magnet.
I had thought about using a magnet several times, but figured it was just to easy and obvious to be a good solution.
Something about possibly magnetizing moving engine parts always seemed like a bad idea to me...perhaps it is just all in my head.