Your presentation is going to be more powerful with props. As well as preparing what you will say, you need to think of what you can show to illustrate your points. Whether you are presenting indoors or outdoors you need props.
You may be asked some tricky questions that ordinarily you might wish to avoid, however, to retain the trust and confidence of your audience, you need to be prepared to answer these questions. Prepare yourself so that you can provide concise, confident and carefully considered answers should this occur.