Re: Better idea
Having looked a little into permaculture, I would have lumped Guinea Fowl in with chickens. And turkeys, geese, ducks, .... I had read they are noisy. I think having more than one kind of fowl is better than just a single kind.
While many chickens eat grain, chickens are also carnivores, and will eat insects and worms. That is how they evolved.
Yes, disease can be a problem. But it is a problem for other animals as well.
One good thing about chickens (and probably other fowl), is that they are quite efficient at turning food into meat (or eggs).