You have to know what YOU like in your wines to decide if you should sweeten or not. I would expect a cab sauv to be dry, so I sure wouldn't sweeten that. The pinot, if you like a sweeter wine... That is your call. How much you add is also up to you and what you want your end product to be.
Instead of adding sugar, try simple syrup. (2 parts sugar to 1 part water. Heat water, add sugar, bring toa boil, reduce heat to a low boil for about 5 minutes,stirring often, then cool.)
We pull almost 1 gallon into a gallon jug, measure a few tablespoons of syrup into it, stir well, taste. (Keep track of the # of tablespoons you add. Leave some of that wine in the first glass, (so you cango back to taste again if needed)then add some more syrup to your gallon jug. Stir well and taste. Continue the process until you hit too sweet. The figure out what you like best, multiply that by 5 (if you're sweetening 6 gallons) and add that amount. If you like it at 6 tablespoons syrup per gallon, 5 x 6 is 30. Add back your gallon and stir it well. If that won't all fit into your carboy, then keep the gallon out, stir up the remaining5 gallons and call your friends for a bottling party. I'm sure you could drink up a gallon of wine in not too long a time!
