We have had guineas for about 8 years now. Congratulations on getting yours. 15 is a good number to give you a reasonable size flock by the time they are grown, since you will most likely lose some to predation (I'm assuming you're going to be providing them with free range area).
We have successfully brooded guineas with chicks in one case, where the hatchery had a few leftover guineas the day we went to pick up chicks. So that shouldn't be a big problem, the guineas will just be more energetic than chicks. Usually, our guineas raise their own keets, with some considerable safety help which I won't go into here. Their range is much larger than that of our chickens and those keets keep up from day one out of the nest, which helps explain why they are so frenetic in an enclosed environment.
That batch had no problem on normal shavings, so we did not experience problems with that or with keet/chick aggression.
The main thing I would say is don't give up on training them. You can train them to coop at night if you do the work EVERY (sorry for the caps!) night. If you are brooding them in the coop, the night work will be easier. Make the coop home. Having older chickens that go into the coop seems to help a lot with giving the guineas a clue. We still go out almost every night to encourage them into the coop...most will go but some like to straggle.
Our adult guineas and chickens have occasional pecking moments but do not fight in any serious way . We do have only hens right now though...guinea males are not too fond of roosters, in my experience. The guineas will likely be their own flock, separate from your chickens.
One thing you may already know but that I just want to emphasize is that guineas seem to need a flock to function well, in a way that chickens do not. Having a bunch (we try never to get below 10, right now it is 17) makes them smarter, and the longer you can keep the flock going by generations, the smarter, and the quieter, they will get as they learn their environment and teach it to the younger ones.
Every single thing you teach these first ones to do (or bad things that you let them do), will get passed on.
For instance: ours are not allowed on cars, or on the house. A scary looking broom or a long pvc pole to wave is good for initial training, don't hit them of course. Holler, wave it, tap it on the roof in question. All our other buildings are fair game. This is no longer something that we train for, it's just something they tell each other, apparently. We still have the pole for those who like to get in the tree at night, and sometimes just picking it up off the ground is enough to make them fly out! Or hollering "I'm going to get the stick!". Pretty funny actually!
Oh, training them with treats and a whistled tune to bring them where you want them are useful too.
Well, I haven't been on the forum for a couple of years but I saw your question this morning and just couldn't resist answering, and now I have talked your ear off, way off your original question about integration.
We love our guineas and would not be without them. Have fun, and like I said, don't give up and never believe for a minute that they are stupid.