Venice FL.

We've only stayed there for a few days this season but Sun n Fun Resort is rather unique. It's huge and the sites are small but they have pages of activities to do right in the campground plus their own bird sanctuary. They have some 1600 sites and they were essentially full last week.

Venice Retreat is next to The Snook Haven Inn.
You can get a water site on the Myaka River.

I, too, have stayed at Sun-N-Fun. They have several levels of campsites. I chose one with a concrete pad and patio, but there are several levels. BTW, the 2011 Edition of Streets and Trips shows it on the west side of I-75. Take exit 210 EAST on Fruitville Rd. The entrance is about 1 mile on the left. Every outdoor activity known to man is available. Here's a link.

Ramblers Rest is the closet full hook up park to downtown Venice, beaches, shops etc. I lived at Sun N Fun for the better part of three years and yes it is a nice park. However traffic is a killer from Sarasota to Venice this time of year. Ramblers is is 15mins or less to the action. Depends how much you want to do at the park or in town. Good luck.