I completely understand the nostalgia of lighting a fuze, seeing a cloud of smoke, and smelling burned powder. With that in mind, however, if there is some kind of safety concern about the powder and/or wadding, why not switch over to a propane cannon?
Much like the spud gun referenced before, a simple mixture of the flammable gas and oxygen can make a pretty significant "BOOM!" without any need for wadding, or the risk of large black powder grains flying out and lighting something else on fire. They are used by special effects crews all over the world, including historical reenactors for the same safety reasons.
Heck, you can even pair it with a large flash pan of powder, if smoke and smell are still considered that essential.