How will you flood the worm bed without causing it to "go anaerobic" and without stressing or killing the worms? Worm castings hold moisture quite well.

The only way to skip the time it takes for the bacteria to colonize the system is to help them colonize it faster. One easy way to do this is inoculate the biolfilter material. This can freely be done by taking a handful of biologically active compost and mixing it with the medium (so as to make contact and smear the bacteria all over the place, the mud might be a fun activity with your son). A more common way is to buy that bacteria in a bottle from a pet store or online. It's not too expensive, a few bucks usually, and can help give a significant head start. The other ways are to regulate the temperature and/or pH to speed up and optimize their reproduction. A pH of 8 or so is best for the reproduction and growth of the bacteria. Typically, a higher temperature (up to a certain point obviously) will speed things up. You will not likely want to manage all that; so, most people just let nature take its course on its own.