Trevor,
I would reconsider and at least test using a 2% bleach/soap solution. Nothing kills mold and mildew more effectively than bleach. If you constantly rinse the surrounding walls with low pressure water while you are applying and letting the mix dwell a short while, it should work fine. Test on a ceiling spot next to a wall first. Unlike percarbonate, bleach kills quickly, AFAIK, on contact, so little or no dwell time is needed.
Surfactants such as Dow's Tergitol NP-9 thicken any chemical mix and provide some "cling". Many PW distributors should carry the product or similar.
Use a clear waterbase wood stain, not an oil stain. Mildewcides in oil stains break down over time, and linseed oil, which is used in most oil stains, is a food source for mold and mildew.