Healdsburg is home to some of the best wines in California. It is far less traveled than Napa or Central Sonoma. It is the way Napa used to be 15 years ago. Great wines, uncrowded, free flowing tastes.
Winery Stops 
This is the first stop off the 101 and is home to interesting whites and reds. They are most known for their Pinot Noirs. Cool thing is that the tasting room is an old barn and there are chickens and animals for the kids to look at.
Beautiful tasting room and grounds and their whites are amazing. Be sure to put your name on the waiting list to join the wine club. It takes a few years to make it through but its free to do so.
Great tasting room and wines with roaring fire for those cool autumn and winter days. The real reason to visit is for the inexpensive white wine and terrific picnic grounds, where the kids can play. Make sure you visit the back room tasting area where they generously pour their premium wines.
Need to make an appointment to taste some of the Valley's most reknowed and respected Zinfandel. The daughters typically host the tasting room which is located in a small area where the barrels are kept. You can taste all the reds (no whites made here) and they always have a nice spread of cheese and, of course, chocolate. You can buy 2 bottles here, which are only available thru the wine club and fine restaurants. Dont miss it.
Off the beaten path but about 10 minutes from Rafanelli. This is a true experience with expansive picnic grounds on a working farm, replete with chickens and cats. This is an all-organic winery and their wines are fantastic. Be sure to check out the L. Preston (red blend) and the can't-be'beat Madame Preston white blend. These wines are not widely distributed so buy here. Of special note, if you are lucky to be here on a Sunday, they pour a jug red blend straight from the barrels. Great for kids, families and picnics. No reso needed.
If you still have the energy, Unti makes terrific Italian varietals. Reds are the specialty and the wines take center stage and there is not much to the tasting room.
They may be the Mondavi of Healdsburg based on their sheer size and the hard-to-follow number of varietals they produce, but the Zins are great. This is kind of like one of the overly-produced wineries that sends Miles apoplectic in Sideways, but the wines are good.
Make sure you pick up a picnic at Dry Creek General Store. No need to go all the way into Healdsburg center to get great breads, sandwiches, cheese, and salads for the day.