My suggestion would be to start with them in seperate brooders (can be as simple as a rubbermaid container) or at least divide the brooder space... they don't have to start with 1 sq ft of space just assume they will by weeks 5-8 that they will need it(whenever you decide to move them to the coop-depends on your weather/wen they are fully feathered).
Once you have them you will be able to tell if they need more space when they start to look cramped, start picking, etc... I suggest two seperate/divided spaces just because you need to be able to tell which of your newest fuzz butts are or are not eating and drinking... sometimes those 2 week olds can push/step on the others because they already know a good thing when they see it! After the newbies start to feather (I move mine together if they are within two weeks of age). Just need to decide if you want to start and finish in one space or add more lamps/bulbs and smaller spaces (rubbermaids etc...) and thin down each group to allow for more space as you go along. Either way will work, good luck and have fun!