Question about hamster litters?

So, my husband and I bought two female DJ hamsters from the local Petco. They were 4-6 weeks when we got them - we had been saving up and gathering items for them for months..it was kind of a big deal to us. So, we FINALLY after hunting all over found two hamsters that had dark eyes not the read tinted ones and bought them after MONTHS of looking. We got them on Halloween so we named them Boo and Pumpkin. We were given a health certificate with them..well about 2-3 weeks upon them arriving in our home Pumpkin, who is white, could be heard squaking at Boo, who is dark, We had been playing with them a lot on our bed letting them run around and what not..putting them in their little balls, we were handling them every few days. Well, it seems like it was all of a sudden we noticed that Boo was growing testicles. So, I took them back to Petco and they informed me they could not take them both back so we had to choose - I can't do that - I have had hamsters my whole life female hamsters and these two never tried to bite or be mean and always came to the cage door when we opened if they were not napping. So, we ended up buying a new cage and since we caught the testicle growth soon enough I was hoping she would not have gotten pregnant..well NO such luck. So, she had her litter of hamsters tonight. We have been feeding her lots of fresh veggies and some fresh deli meat and turkey if she wants it and boiled eggs if she will eat it and of course lots of hamster food, lots fresh water, bedding...and so forth..and we put a blanket over the cage and plan on shutting her in the room alone during the day while we are at work...less noise. But my question is this. We don't know how many she has had..but i'm assuming it was atleast ten....it sounds like a lot when they squeak. My question is can I keep a few females and put them in a cage with mom? And how do I tell which is male and which is female PRIOR to them growing testes?? I read on teh internet that you have to measure the cloaca and anus and the ones with the furthest apart are boys and closest are girls..but obviously Petco screwed that up is their another way?