I have guineas and in time you will be able to tell. They have red things on their checks , the males will be much bigger and the helmets and the hens are small and so is the helmets. There a great web sight that will tell you everything you want to know It is a great site. I guess just googled it. I have around 11 now started with 17 but lost some a long the way good luck with yours.
I did do some googling