My DD is in daycare during the week so it's only on weekends that I have this dilema. I love to go out but at the same time I try to be sensitive to her naps. Like others, we try to go out first thing in the morning and be home around naptime. However,she always falls asleep on the trip home, so we've always had to transfer her otherwise if left in the carseat, she will short nap. Most of the time, the transfer is sucessful, but there are times that she'll wake as she is not a heavy sleeper. We usually leave her in the crib for as long as she'll let us and most of the time she'll fall back asleep. If she doesn't nap, then we APOP a car nap later in the day.
If we have to meet a friend for lunch around her naptime, then we APOP a short car nap before and another one after. It helps that the car puts her to sleep. If we have to meet for dinner, then I usually suggest an earlier dinner, like 5:30/6:00 PM. My friends usually understand.