I am actually eager to know that exactly how will you launch them
With the existing systems they just produce gas, and virtually no visible flame, so its hand-launched and is not dangerous. A propellant for something like this would have to have extremely fine ingredients, large mesh charcoal or metal powders are a bad idea unless you want to set your clothes on fire!
I was thinking along the lines of a small sugar rocket end burner, they don't need to provide much thrust as the 'plane is already up to flying speed from the hand launch. The rudder is generally trimmed slightly to the left or right so that it doesnt fly too far away, just round in a circle. It should be launched into wind, to gain height as early as possible (small core to provide more initial thrust perhaps), to give a longer gliding distance. I've been planning to build something like this for over a year, but have never really had the time.
There are a couple more options with these too, whether to go for a high thrust, small wing diameter plane which will travel quite fast, or a low thrust but longer duration glider-style plane.
Using a standard balsa and tissue covered wings model, the motor must be mounted well out the way of the wings, as the tissue shrinking dope is basically NC lacquer (comes in handy when you run out of ping-pong balls) and will ignite at quite low temperatures.
You can never have a long enough fuse...