I've lived in Jacksonville for three years now. My husband was born and raised here and his parents have lived here since they were small children. I really like the area.
There are a couple really awesome holistic/natural parenting friendly pediatricians in town. There is a great homebirth midwife and her back up OB is great as well if you prefer that route in case you are planning on more kids. There are several active LLL groups in town and a big natural birth community.
I know there is a good AP group although I am not involved with them.
As for things to do with kids, there is the beach of course but there is also a great zoo. The Museum of Science and History is very nice. There are lots of nice parks in town and most of the movie theaters do summer free movie programs. www.jax4kids.com
is a very helpful website!
There is decent shopping and good restaurants. We get some good concerts but not as good as Atlanta. There is a decent theatre scene and the symphony is supposed to be great if you enjoy those types of activities!
Housing does seem to be getting expensive. But right now is a buyers market because they have built all of these homes and no one can sell theirs quickly so there is a glut of houses. You can find homes with acreage on the north and west sides of Jacksonville, as well as just south Orange Park which is another town that is part of JAX metro area and is on the SW side of town.
I hope that helps some!