You can buy an all-purpose poultry feed that covers both chicks and keets. I personally am brooding them separately, with the chicks getting starter and the keets getting game bird food. You can house them in a coop together later, just make sure you have roosts. The guineas like to be up high. Doesn't matter the light color, but I choose red when I can. It is supposed to be less stressful for birds.
Edited to add: Be weary of the Guin-hen which is a cross between a guinea and a chicken (also called Guins). If they are housed together and you have males of either sex, hybridization can happen.