I have no path suggestions.
It is not too different with the TAB. It feels kind of like someone is tugging on your bike. Probably the biggest thing is for your son to not wiggle too much. You'll feel it and it can affect your steering. It is not too bad, but you would not want it to happen in a tight situation. It works better when they understand that they can't safely jump all around back there.
Take is slow in the beginning and both of you will build confidence. My biggest worry at the younger ages is that they will fall off. It has not happened yet but it is my biggest worry. I frequently ask how my younger ones are doing because their hands get tired. As soon as they say that they are, we take a little break. I take the trail and distance into consideration so that they have enough in them to hold on for the trip. To give you an idea of distance you can do, my just turned 4 year old can do 10 miles with 1-2 breaks on unpaved paths\trails. Last year I would have to rotate them.