I think you did good, regardless of neighborhood, etc, although with several folks in the car, the chances of him wanting to carjack diminish. But this kind of stuff is spreading out to the safe 'burbs and they are getting bolder. And those are exactly the kinds of ploy they use in the approach phase: got the time, do you know where there's a MacWendyKings?, which way is Blergsdorf Street?
Your Dad may need an education in street smarts. Take a look at Pax's "The Conered Cat" site for descriptions of the various phases leading to an assault.
You could have brought a pencil along and sharpened it with long, slow, precision strokes while grinning evilly at him.
Same kind of thing happened to me in front of my bank last summer...I noticed a guy hanging around outside, and when I came out I sat in the car organizing all my little receipts and such. I had my .380 in a belly pack, and as he approached, I unzipped it and reached in, clearly showing I was armed, without actually showing the gun.
When he got to my car window and started to open his mouth, I interrupted him by saying loudly, affirmatively, and baritonally, "I have nothing for you!" and moving my hand, gripping the .380, inside the belly pack.
He said, "Oh, sorry," and moved away quickly. I realize I should not have let him get that close to my car in the first place, but, after all, there are social niceties which conflict with a defensive mode of thinking.
This technique of interrupting them seems to short-circuit them. I use that a lot with the panhandlers around LoDo (Lower Downtown Denver). I am the most generous of persons, but I won't give them a dime or the time, or a cigarette, or a light, or directions, or anything.
Besides, most of the panhandlers probably have a net worth greater than mine. Theirs may be zero, but mine is negative.