Pregnant mouse!!!! need lots of help!!!!!!!?

ok i just bought 2 female feeder mice from ABBA PETS about 2 weeks and 1/2 ago.... now both of them are getting really plump around their bums.One of them is allot fatter than the other one(her name is rain)her friend is quite a bit skinner.i know they are both pregnant and that is why i am worried about the skinny one(skittle)i read that from the date of conception it takes about 21-24 days for them to give birth and u only notice a weight gain in the last week of pregnancy so they should have their babies soon.since rain is larger, does that mean she will have more babies? also some tips on wat to do with the babies if they have allot? i tried the cage calculator and it said i could have 11 in my cage at max. i have 2 in there now and i will but the males in a smaller cage till i find someone to adopt them. i WILL NOT take the females back to the pet store because the owner keeps the males with the females and he said there is allot more males than females.