Since I am sometimes asked for my advice about this, here are what I would say are the most important points. If it is YOUR group, then YOU decide how things will be done, and you should only enlist people who will cooperate. You may have to modify your goals and methods now and then, but in a real democracy you and your ideals could be trampled too easily.
Democracy is also conducive to factionalism and long meetings.
Explain your chosen form of government clearly to all potential members, and tell them what they can expect and what is expected of them. Give them the option of just being associate members so that they can still learn and keep in touch. Some aspects of the organization might be left to the membership's decision, for instance, do you all want to portray the same thing, or have each member portray a different troop type, era, etc. Publish a newsletter regularly, at least every 2 months. If the majority of your members have email you can do an electronic newsletter and save stamps.