The one thing I will say about inductions is that it is a completely unique experience from one birth to another and one woman to another - what you went through last time may not happen this time regardless if baby is bigger or not. Also subsequent births can sometimes be easier as the first one has 'paved the way' so to speak. usually shoulder dystocia is a positional problem too - try some exercises to get this little fella in the optimum position for birth will help you immensely as will the positions you use during the birth. If your Ob is keen to induce at 38wks then naturally he will be smaller than if he was left to term too. One other thing is that he will be two weeks early - not always an issue but if he isn't ready to be born then sometimes that can bring it's own implications.

Good luck - I am sure the decision you make will be right for you.