If you're wanting to go bioactive, you might want to wait until your snake's mite-free. Think of it like giving yourself the best chance of succeeding.
There are some other threads going on right now about mite treatments; I think you'll just want to use paper towels as substrate for the time being. They might have come in on the aspen, but fortunately you can put some on a pan and bake it on a low setting (around 200-250F) for a few hours. That should get rid of any mites hiding in there.
You can use this opportunity to let your new setup grow in and let your isopods and springtails get their numbers up for when your snake is ready to be added.