Gingerbread Stout

So I have a request from a non-beer drinker to make a Gingerbread Stout for the holidays. As i'm not sure how big of a fan of it I am I was thinking of making a stout and split the batch between two 3 gal carboy's.

Every recipe that I've come across has the spice's added as a late addition to the boil. I'm curious if I would be able to use the spices in a secondary and rack on top of them or if there's a different way to get that flavor is just half a batch.

You can make a tincture ( spices soaked in neutral spirit like vodka ) and dose at bottling/kegging. That way you can get just the right flavor you are looking for. If not, then secondary would be you best bet. I've never had much luck carrying off flavors from the boil. Either way, start small and add more if needed.