Hi Toni. There are many ways to conduct this type of training session. Of course, the first (and probably most important) issue to resolve when conducting partner training is whether the two people have similar fitness goals and fitness levels. This would go a long way in making the session enjoyable and challenging for each participant, AND easier for you to administer.
You can create ‘mini’ circuits in which the participants rotate through them, taking turns at each station. You can have them perform partner exercises such as medicine ball tosses. You can have each of them perform the same exercises at the same time (such as stability ball leg curls). Any of these types of set-ups would provide for a great training experience for your clients.
I hope that this helps.