oh my god, possibly 9 pregnant does-HELP!

well today i went to collect my new mice, all went ok until they brought out a tiny tupperware type tub complete with a lid with a few holes punched in it, condensation was running down the inside of the tub and the woodshavings were so wet you could wring them out. inside when they opened it up, 10 little faces peeped out at me, well i wasnt leaving them in there, so i took the lot. they were soaked through and werent putting up much of a struggle when we caught them. there was a minimum donation, so we paid £5. i would have felt so guilty leaving them there. now they also had another cage, proper cage, with the male mice in it, and i asked them time and again are these all female, definately, and the lady kept saying yes they are all 100% does. ok, so i figure, take them home, i have another spare tank, a 2foot x 1 foot instead of 3 foot x 1 foot, and i can split the group when they are a little bigger.

:shock: i am getting used to my new little furry buddies, and ive pulled them all out, they are so much more lively, and are constantly on the go with the wheel and toys instead of just burying themselves in the floor. well im looking, and 1 seems to have a bulge, it looks like there is a mickey in with 9 minnies, i did notice that the females are plump, but they have devoured 2 full bowls of food since they arrived. now im thinking i could have a massive problem on my hands. i cant sex them, they are so wriggly and jumpy as they havent been handled, but ive tried and think ive looked at every single one and all the what i think are females have close together bits with no swelling between, then theres 1 brown and white one, who when it sits on the edge of the food bowl, looks to have something hanging, and im pretty sure its testicles, i watched as a second mouse sat there and it didnt seem so bulgy down there even though they were sat the same on the edge of the bowl. should i split him from the group, and if i do will he be ok on his own?