The courthouse is a public building so children may enter. But it is always best to make other arrangements for your children if you can. If you have a court hearing, it will be very difficult for you to concentrate on what the Judge and witnesses are saying if you are also trying to watch your children.
Also, sometimes you must wait for your case to be called and children may get restless and noisy. This can interfere with the operation of the court. Most importantly, Judges do not believe that children should be exposed to many of the issues and arguments about family issues that come up in the courtrooms.