Dud eggs

Question
I just brought home two Social Finches,I got them a nice house with hay now I have 5 eggs. i have no idea what I'm going to do with 7 birds if they all live. Could you tell me if there is a way to tell the male from female? one has what looks like a toupee on and the other dose not. when the babies are about two months old can I separate them? how can I tell the males from the females? Also I would hate to separate the parents, If i keep them together and if they have more eggs could I remove the eggs and put them in the frig over night( to make the a dud) then put them back so not to stress out the parents? and if so how long can they sit on them? And could they still have more eggs while sitting on them?

Answer
Sorry for the late reply, I didn't realize my answer didn't send!
The only sure way to tell a male from a female is through DNA testing however you can also check the vent of the birds. If there are long "feeler" feathers around the opening, it's a male if not it's probably female.
The babies can only be separated after they are fully weaned and eat seed on their own. This is usually two months after they first leave the nest. It's impossible to tell the gender of a fledgling without DNA testing.
Since they are Societies, you can leave the babies with the parents even after the parents have more eggs without having to worry about fighting. Keeping eggs in the fridge over-night is perfect and leave them in the nest for a couple weeks before taking them out of the nest all-together. Just make sure you mark the eggs you've made duds in case they have more.
The female will usually lay one egg a day and approximately have 6-8 eggs with 1-4 being fertile. After she is finished laying eggs, she will not late more while she has those ones.