I'd recommend a simple, safe flight near the airport doing something basic you are well-familiar with. Your confidence and skill will improve over time, but I recommend keeping it basic at first.
This is true regardless of your experience level as a pilot. People in general aren't super comfortable with small planes. Keep in mind that they're inexperienced passengers too!
I've found that the best "intro flights" for pax go like this:
1) Show them and talk them through the preflight inspection. That helps to give them confidence in the machine, as well as reassuring them that you know what you're doing.
2) Give them a briefing!
a) Ask about their experience on airplanes before - I have taken some people who had never even been on an airline flight, and they didn't know that airplanes bank when they turn, and the first such person I took got a little freaked out by it. As a result, I'll talk through all that sort of thing beforehand if they've never flown before.
b) If they have been on an airline or other flight before, let them know that you're going to give them the same safety briefing information and that it's required for everyone. That should help keep them at ease when you start talking about what to do in the event of an accident.
c) Talk to them about any potential turbulence and what causes it. I think a large part of the reason people find it uncomfortable is that they don't know anything about it and it seems dangerous. That said, try to do these intro flights when turbulence isn't as much of a concern. Avoid late afternoon on a spring day, for example. Also avoid any time where heat will be excessive.
d) Keep things light - I like to tell people that they need to have their seat belts on for taxi, takeoff, and landing, but that they should keep it on the whole flight because there's not exactly anywhere they can go! Another thing I like to say is that "aviation is always an adventure, it's just not always the adventure you planned on."
e) ***MOST IMPORTANT!!!*** I like to tell them that the purpose of the flight is for them to have fun, and that if at any point they're no longer having fun, to let me know and we'll come back and land. It gives them some control over things. I think a lot of people's fear of flying is rooted in the lack of control, so allowing them to have some control really helps.
3) Pick one or two local landmarks as well as their residence to fly over. Take off, go to each one, avoid more than maybe two 360s to avoid motion sickness with inexperienced pax, get back to the airport and get on the ground before they even have a chance to think about being afraid.
4) Know where to point them if they want to take lessons afterwards.
