how do you guys handle riding with someone who is significantly less in shape than you? here's my situation:

My dad loves to ride. Has ever since he was a kid. Unfortunately, his work takes up all of his time, and he rarely gets to ride, and when he has the time he's always very tired. Luckily, today he had both the time and the motivation, and I had the pleasure of setting out with him (some details on my bike blog)on his beautiful blue allez comp (needs some adjusting, but that's not the point). Anyway, having ridden with him before, I knew I would unintentionally set a pace that would be too fast for him, so I let him lead. A few minutes in, I was casually drafting when I realized that I was actually making the ride even easier for myself, instead of leading and having him draft off me.

So here's the question: would you lead, concentrating on keeping the pace slow and letting them draft, or would you let your partner take the lead, and encourage them from behind?