Saying that sociology derived from the Enlightenment is akin to claiming that the iPad evolved from the light bulb. Although one might have derived from the other, it's a very long, thin, and tenuous connection. The Enlightenment, as a philosophical movement, encapsulated such new philosophies that humankind was forever altered, for the better. Certainly the concept of "Social Contract" is first seen during this time. But if sociology is the study of the development, structure, and functioning of human society, the study of social problems, there's a critical difference between that and what the Enlightenment Philosophers were concerned with, among which were: "What is an individual's relationship to the church and to the state?" ""How does that individual function economically?" These concerns were focused on a "bottom-up" view, from the individual to the culture at large, as opposed to a "top-down" view, which sociology incorporates. The fact that it relies upon statistical measurement of how groups of individuals interact belies its difference in philosophy. Certainly there is value in rationally analysing how groups interact; however, there's danger in trying to implement upon the culture what some believe to be a correct analysis of a problem. "One-size-fits-all" approaches rarely succeed.
There were many different strands of Enlightenment thought. While I wouldn't dispute that locating modern sociological theory and practice within the Enlightenment tradition is somewhat ahistorical, I think that claiming that Enlightenment thinkers all thought there "was only one right answer" oversimplifies the diversity of the Enlightenment, and certainly doesn't take into account the thought of philosophes like Diderot, Voltaire, and especially the abbe Raynal, who were in many ways what we would recognize today as cultural relativists. Montesquieu, as I mentioned earlier, was essentially the founder of social typology, even if he did believe in universal natural law. German Enlightenment thinkers, Herder and Humboldt in particular, argued pretty explicitly that culture was related to environment. Smith's Theory of Moral Sentiments is based on the idea that one's understanding of ethical behavior is formed through human interaction. Again, none of these people even approached the sophistication of modern sociology, but I don't think we have to look that hard to see some of its roots in eighteenth century thought.
Whilst I agree in part with #5, at the same time I also think that Sociology and the modern discipline of social science as a whole was built on the foundation of the Englightenment in so many ways. Let us remember that the Enlightenment was about the scientific method and the application of this method into all aspects of society. In this sense, Sociology as a subject can be seen to be the descendent of this Enlightenment approach. I agree with #4 in identifying Voltaire as an author whose thoughts about religion definitely helped to precede a sociological view on this subject.
I hate to be a contrarian, but sociology as a field of study is much much later than the Enlightenment. For this reason, sociology in many ways is a departure from the Enlightenment. It is the idea that each society has its own inner workings, that we are shaped by culture and that we make culture. It also goes against the presupposition of the Enlightenment that there is only one right answer and something called absolute truth.
I think Montesquieu would be perhaps the best example of a proto-sociological thinker. He created "ideal types" in analyzing the types of governments, a concept that is at the heart of sociology, and he recognized that within these types of government, people would need to interact and behave in different ways. Voltaire's and Hume's (more Voltaire's I think) writings on religion also anticipated a sociological understanding, as did Adam's Smith's recognition of economic transactions as social acts. Smith also pioneered a sociological/psychological approach to how humans define moral behavior in their relationships.
In addition to number two's response, the Enlightenment scholars' biggest contribution to sociology was the idea that the world COULD and SHOULD be better. Until then, everything was accepted as God's will. It was revolutionary.
The major Enlightenment ideas that shaped these perspectives were A) that things are caused by factors that can be understood scientifically (as opposed to being caused by God, for example) and B) that logic and reason could be applied to improve society. These ideas led to the beginning of sociology in that they encouraged a systematic and (it was hoped) scientific study of how society comes to be the way it is.