Sound's good, use some biscuit malt to get the graham cracker flavor (you will need to do a mini-mash for this), with a bit of vanilla added in secondary. Or you could just toss some s'mores into the fermenter.
my friend wants to make a burnt marshmellow porter. talked to him yesterday and he was boiling some corn syrups to get the marshmellow flavour.
Dunno about wise but it can be done. I looked at some nutrition labels and graham crackers are about 20% fat, calories-wise. Oats are 15% and they are used quite often. My hunch is that most of the fat would be utilized by the yeast or would sediment out. Some would be caught in the mash filter bed too. Shelf life wouldn't be terribly long, but it might be an interesting novelty.
Graham cracker in the mash will work much better and cleaner indeed. I'd give that a try actually. Chocolate wouldn't be hard, add chocolate malt, pale and regular and maybe some chocolate in the boil, or nibs in the primary/secondary to age on for a wee bit. Id some lactose obviously to get back some residual sweetness. Marshmellow... no idea. I hate 'em.
I brewed a s'mores milk stout a few weeks ago. 1.068 o.g. 38 IBUs. I added 2 boxes of graham crackers to the mash, took my first runnings and mixed it with 2 bags of jet puff marshmallows and then added it back in at the whirlpool, and I added 4 ounces of 100% cacao bakers chocolate at the end of the boil along with 8 ounces of Malto Dextrin and 1 lb of Milk. Sugar. It was fermented on Wyeast 1056 and ripped through fermentation, most likely due to all the extra sugars. I am going to rack it to secondary on cocoa nibs and a bourbon soaked vanilla bean. Hope that this helps a bit. Let me know if you want to know anything else.
Generally not my thing, but BaseCamp makes one that is actually very good if your in the mood. Maybe contact them for pointers. http://basecampbrewingco.com/beer/
I'd toast some marshmallows and toss them into the boil at about the 5 min mark, might get you some of the flavors your looking for.
My brewing partner and I have made a S'mores stout that has won some medals. Constantly tweaking the recipe, I can say graham in the mash provides no graham flavor or aroma to the final product. Last batch we used marshmallow and graham flavor extracts in secondary, added flavor and aroma we were going for but a slight chemical flavor taht took a few months to fade. We do corn syrup and brown sugar slightly caramelized for the marshamallow and vanilla beans in secondary. Mess around and have fun with it, we love our version every time.
I believe we did 1/2 teaspoon of each, along with the split vanilla bean. This time we will be upping the vanilla bean and trying graham cracker in secondary with way less extract to see how it turns out. I love the experimentation part of brewing!
