Cider is fermented out - what next?

The situation:
I have 5 gallons of fermented cider that has been conditioning/clearing in a carboy for about a month now and I am ready to keg it. I let it ferment out completely so obviously it is very dry now. This is for my wife and she prefers her cider semi-sweet.

I am looking for advice on how to accomplish back-sweetening the cider before force-carbing it in the keg. I plan to stabilize the cider with potassium sorbate before sweetening but I'm not sure what my actual process should be. Should I rack to the keg, stabilize it, add some apple concentrate and then carb it up? Is adding a can of apple juice concentrate, or several, to the keg after racking a pretty tried-and-true way to do this? If so, how many cans would you suggest for a nice semi-sweetness similar to something like Crispin Original (my wife's favorite)?

Any specific details you can provide for the best way to go through this process would be much appreciated.

My method with wines, which are still, is to rack to a new carboy (off the yeast et al), stablize and sweeten at the same time and let sit for a week. Check Gravity before and after week. If gravity has changed, then fermentation is going on, and more agressive methods might be needed, if not, rack to keg. (well my case, bottle).

I'd suggest if you are ok with sulfates, that you use 1 campden tablet with that along with the potasium sorbate. both Meta-k and k-sorbate don't kill live yeast, they both inhibit further growth. One prevents reproduction adnI forget what the other does. Also cooling to help drop the yeast and pectin to help clear haze (which will help drop yeast) The goal being to clear as much yeast as possible, because the yeast can over power the stablizers