Well, first you will have to explain what airsoft is, because a lot of people do not know. Also be sure to emphasis safety procedures etc. And since you can't bring equipment with you to show everyone, have a powerpoint ready or at least some enlarged pictures. Be very careful on what words you use. Meaning do not use words like Kill, war, battle. Tone it down for the public, because public opinion means a lot. BUt feel free to use airsoft terms as well, just make sure you explain everything in a nice way (And it would be a good idea to post your speech on here so we can read it and help out further).