My experience has been that most kids are fairly harmless and most of the bad behavior can be attributed to too much enthusiasm, energy. etc. If behavior needs to be corrected, it is usually easy to do - especially if you spell out very clearly that the specific behavior is the problem, not the child. Such rules as are necessary should be applied equitably. Fairness, compassion, understanding, empathy and a sense of humor are essential. We tend to remember the problem people, whatever age, more than we remember all the people who were behaving nicely.
Adults often behave more combatively than children do.
Many libraries, due to funding problems, don't staff youth services areas at the same level they staff adult services. This baffles me - children are often in need of more support, assistance and direction, but aren't apt to receive even the same level of service as adults demand and receive. The public library is a progressive democratic institution. Time for another library land slogan - libraries are the people's universities. Public libraries serve a larger portion of the community than just about any other local government agency.