DO NOT use any sort of oil, olive or otherwise, on your snakes. Mites can be drowned by placing your snakes in a tub with luke-warm water to which one or two drops of detergent have been added. They drown easily, and you can leave the animals in the water for 24 hours.
Remove the snakes from the water, and place in CLEAN, freshly washed bags (pillowcases) until you have cleaned the enclosures and the room in which they are housed. Remove and destroy any cage decorations, remove substrate (paper, pellets etc) and place in a plastic bag and place in the sun for the day so it gets really hot and kills mites within.
Spray the entire enclosure(s) inside and out with a solution of Orange medic and water, 30%/70%, and leave to dry, then wipe out, disposing of the rags or paper towel using the plastic bag/sun method.
Wash waterbowls and anything similar in very hot water and detergent.
Depending on the size of the room, buy one or two insect bombs with residual effect from the supermarket, use these in the room as directed, with your enclosures open, and you will have no more mites (until someone kindly passes them on to you again). These 'bombs' contain a non-toxic hormone growth retardant which prevents the mites from developing into adults, and this lasts around 6 months. The initial 'spray phase' contains pyrethrum or permethrin which knocks the live mites off - once the enclosures/room have been aired off, the residue won't harm your animals.
You MUST be thorough and very careful not to contaminate the cleaned area with anything that may have mites remaining from your cleaning activities - rags, paper towels etc MUST be disposed of carefully, and clothing must be washed immediately in hot water.
If you aren't thorough - they'll come back and be a persistent and very damaging problem.
Quarantine, quarantine, quarantine...
Jamie