..or maybe he would just like to see a new dojo appear so that more people get to enjoy aikido....
That said - teaching is the greatest teacher for most of us.
Being a 3. dan I would expect that you have quite a bit of experience teaching and participating in demo's... no? well have no worry..
I would suggest that you put together a simple program that shows the major groups of techniques that you practice in your line of aikido. Throws, weapons, warm up drills etc. Show them what it would be like to practice with you. Don't dassel them too much... just plain ol' simple and beautiful aikido.
If you don't feel comfortable just talking then prepare a very short speach that you write down and rehearse over and over. Just tell them briefly what aikido is about, what you emphasize in you dojo, where, when and how people can practice with you - and thank them all for showing up.
You might suggest writing a text about the techniques you are going to show. Having a narrator reading this aloud during the demo is a really cool thing. But it takes quite a bit of work writing it down, and you need a person to read it, who has a good voice and enough knowledge about aikido to tell the rigth things at the right time.
Oh... and make sure you have at least one good experienced uke that will make your technique look good... Import if neccesary.
Finally... remember to have fun
- Jørgen Jakob