Apple Pie Ale

I am planning to brew an apple pie ale for my family at Thanksgiving. Just a fruit beer for the family to enjoy and try something unique. I was planning on using two quarts apple cider for flavoring. My question is:
a. Do I substitute 2qts of water in my initial boil for the cider?
b. Do I boil 4.5 gallons and then add 2qts cider?
c: Do I ferment 4.5 gallons and then add 2qts cider to my keg?

Each option might have its own advantages. Anyone experienced in this area. I have not tried this before.

My concern would be how all that sugar in the cider effects the gravity. 
I'm interested to see what others have to say.  IMy thoughts would be to boil it and add it to the keg, plus some spice in the boil to give it the flavor you are after.

My initial thought would be to refrigerate it. Boil 2qts less than the recipe called for and then us the cold cider to drop to the final temp temp at wort chill. That way the sugar would ferment out and add a little ABV kick to the beer. Just an initial thought.

Having just tried something similar using cranberry juice, I would recommend using concentrated apple juice to give the apple flavor.  You will use a lot less of the concentrate to get the flavor you want and can top off before bottling if you want it to be stronger (just back off on the carbonating sugar accordingly).

I made a Pomegranate/Cranberry ale recently.  I made a 10 gallon batch of wort.  In 5 gallons of the wort I put pure juice (32 oz each of pomegranate and cranberry) in with 10 minutes left in the boil.  My starting gravity was 1.063. 

The other 5 gallons were a gingered beer, with spices but no extra sugars.  The starting gravity was 1.046.

So, that may help you estimate the gravity.  My gingered beer went down to 1.009.  My pomegranate/cranberry went down to 1.004.

The ABV of the gingered beer was 4.8%.  The ABV of the fruit beer was 7.8%.

There was plenty of fruit flavor, but not overpowering.  I did end up with about half a gallon more at bottling with the fruit juice beer.

My last cider experiment involved five gallons cider, a few pounds LME, and a package of US-05 dry yeast.  I dissolved the LME into some cider on the stove, and mixed it in to the rest.  After it failed to take off I realized I never warmed up the refrigerated cider, so I placed the bucket over the heating vent until it got up into the seventies.  After fermentation I force carbonated it in a keg.  It came out good, but holy cow it was dry. And astringent.  Like, pucker up time.  If I do it again I'll treat it with potassium sorbate after fermentation is complete, back-sweeten it to taste, then carbonate it. 

Based on that I have a couple of thoughts.

First one is that cider ferments out bone dry, so don't count on any residual sweetness from it.

The other is that cooked apple tastes completely different than fresh apple. So I would not boil it.  I'd suggest treating the fresh cider with crushed Campden tablets (available at any LHBS) and adding it to the chilled wort after the boil. 

Two quarts? I'd use a gallon. And maybe a dash of pumpkin pie spice.