Hi John.
The Canyon du Verdon is absolutely lovely and as John said, so is Castellane. If you do drive all the way along the Gorge to the lake of Sainte Croix, travel out along the road on the southern edge and back via the northern road. As you will be driving on the right, this will give you by far and away the best view. If you only drive part way along, use the southern road, the views are good all the way whereas the northern road has some very impressive rock overhangs for the first part of the journey but it's less attractive the further you go.
Also, if you do go all the way, try to make time to visit the little village of Les Salles de Verdon ( perhaps for a mid-day snack ). Although it's a new village ( the old one was is now under the lake ), you can get down to the water for a swim. In fact we stay Camping les Pins on the edge of the lake rather than Castellane but it's not so convenient to get to - as we're retired, time isn't quite so important. Their website is .
http://www.campinglespins.com/
At Annecy, most people would suggest Camping la Ravoir which I understand is quite good but the pictures of which are quite deceiving in regard to it's access to the lake.
http://www.camping-la-ravoire.fr/accueil.php?lang=EN
You might look at .
http://www.campingaucoeurdulac.com/cacdl_home.html?L=1
this has direct access to the lake, has a private gate onto the fantastic cycle track, is close to Annecy, is a few minutes walk from a boarding point of the lake steamer, is a two minute drive from one supermarket and is only a few minutes walk to a Lidl.
Again, if you drive round the lake, drive clockwise for the better views.
With regard to traffic conditions, enter your route onto the Michelin routeplanner the evening before you leave and in the subsequent driving directions they will warn of road works and being a French company, such information is bang-up-to-date.
Have a good trip.
Olly.