Follow the directions on the BK-II canister PERFECTLY. That stuff can be dangerous if you use it wrong, but it is extremely effective.
Take all the porous materials out of your snake cage - use only papertowel and plastic/ceramic/whatever in the cage until the mites are totally gone. Soak the snakes while you are treating the cage; mites can't swim. If you can, get reptile relief as well and treat the snakes themselves with that (again, following directions on the bottle).
I would use the BK-II once a week until you are absolutely certain all mites are gone.
Snake mites are specialized mites that only affect snakes (hence the name 'snake mites'). They won't go after people - you might find them crawling on your skin after handling the snakes, but they're not going to bite you. Whatever is biting your family is not coming from the reptiles!
~jenny
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
"I have never made but one prayer to god, a very short one: "O lord, make my enemies ridiculous." And he granted it." - Voltaire