Robin, he will learn to fall asleep in his bed if you allow him to learn. As long as your driving him around, he's never going to master this very important skill. What you will find is that one day, he may scream all the way through nap time. So, as long as he's not hurt/hungry/in need of a diaper change, he will either fall asleep or not. The important thing for him to realize is that your not coming back.
The next day, he may scream again.
And maybe the next.
But the day after that, he'll finally fall asleep. He may not sleep for an entire nap, but he should sleep.
And, the day after that, it will be even easier.
And, easier and easier.
I have one right now that I'm teaching to fall asleep. Trust me, I've been there, several, several times. And they do get it and turn out to be great sleepers.
I took care of a little boy from 10 weeks until 5 years old. He learned to sleep at my house and did so for all those years. I truly believe that he had the best "quality" sleeptime at my house. At home, he wouldn't sleep in his own bed, would get up when he chose, fall asleep where he did.
It will be much harder on you than on Ian. And you might find that within a week or two, you truly have some down time to your self.