Read the thread 
Raising Guinea Fowl 101 and pay particular attention to posts made by 
@PeepsCA .
Guineas are a flock bird and do best in large groups.  I never recommend getting fewer than 10 guineas.  They need a high Protein turkey or game bird starter for proper development.
Guineas can be sexed as adults.  The hens will be able to do a two syllable "buckwheat" call.  The males will not makes this call.  The females can make all the calls that the males can make.  When a guinea hen lays an egg, it is proof positive that she is a hen.  Guineas do best in a ratio of 1 male to 1 female.  Some males may prefer to have more than one mate.
I do not recommend brooding guinea keets with chicks due to the problems that imprinting can cause when they are mature.  I don't recommend housing them with other fowl either.