I'm really not sure what the "chinchilla scene" is like where you live...if there are other options available such as a chinchilla rescue or whatnot...
If your primary concern is money, then you'll need to house them until you can sell them. If the petstore is willing to pay in this case, I'd sell them the two males together...as has been stated, BOTH females could be pregnant and either scenario may be from inbreeding.
If money is not the concern, reduce the price to sell them quicker but again...unless the buyer has baby experience that'd be VERY irresponsible as (again) both females could be pregnant. So (again) selling the males together would be the best option.
Your other option, if money isn't the concern, would be to give the whole group to a chinchilla experienced rescue.
Finally, and it can't be said enough, these chinchillas should already be separated. If you don't have time to care for four...imagine caring for 8 when the females litter...and they will...as males and females breed. Period. They don't consider whether or not they're related. They can't think on that level.
SO, unless you have an immediate and RESPONSIBLE rehoming option, please separate males into one cage and females into another (and babysafe) cage.