As I was spraying down the tank I noticed a LOT of tiny white mites crawling around the substrate witch I am fairly certain are predatory mites. But also I see the odd tiny creature that looks kinda like a cricket but is VERRY small. could it be a pinhead? or possibly some kinda mite? it jumps around and seems to move like a cricket... strange...

If it is a pinhead cricket could it harm the scorp?

white mites are cleaner mites. not usually a problem but make sure you keep up tank maintenance otherwise they can soon get out of control.

Tank maintenance: ensure husks / uneaten live or dead crickets are taken out
(you could use woodlice(pillbugs) to help clean these up - they love to eat mites, mould and husks and wont harm the scorpion)

secondly it is more than possible to have baby crickets in your tank. they usually get there by females laying their eggs before the scorpion eats the cricket... or if you have fed a nice fat female to the scorpion eggs may have dropped out during the eating process. Ensure you twist the female cricket ovipositor before feeding to the scorpion

the pinheads will die out with no food - feed your scorpion male crickets and they will also eat the pin heads before becoming lunch!

where can I buy some of these woodlice/pillbugs?

Grab some from your backyard, let them live for a generation or two in their own terrarium to ensure no residual pesticides / parasites, and there ya go.

The tiny hopping things are more than likely springtails. Pinhead crickets are very obvious that they are crickets (the legs and the antennae are dead giveaways).