Yeah, most of my beginning information was garnered from pet mouse breeders too. And I can understand their position as well..its just that when I breed for fun and for snake food, I have to walk that fine line between them both. I don't want to be too soft about it, nor too harsh and careless.
I have never had any mother reject or cannibalize after I've handled the babies. I take from all stages of their development, not just pinks. I generally grab the entire litter out of the colony and place them in a bowl. I take the bowl over to where the snakes are being fed at and scatter and sort through them like a bunch of marbles to get the size appropriate for a particular snake. If any are left over, I just dump them back in the nest spot. The females will come back over and inspect and clean accordingly.
Every once in a great while, when I dump the babies back in..one female gets it into her head that she should move the babies because they'd been discovered. So she'll pack them one at a time to some other spot in the cage and the other females spend their rest of the night putting them back and so on and so forth. Usually if I see that, I'll take the babies out for an hour or so to give the females time to calm down and my scent time to wear off and I'll dump them back in. Usually in that time frame they tend to forget what they were doing an hour ago. =P
But that's the beauty I love about having my own feeders. If I don't use all of the pinks I had, I just put them back to grow more and use them at another stage. No more wasting pinks in the trash.
Sexing can be tricky, but with a little patience you'll soon master it. I never sex newborns up to a week old. Their genitalia hasn't differintiated enough for me to tell the difference. By the time they've got a good coat of velvet-like fur and they're incredibly chubby...that's about the best time I've found to sex them. At that stage, the female's nipples will stand out like buttons on a coat..the males don't show this. Also at this age, the males testicles will have started to drop into the scrotum and are more easily recognizable. The space between the anus and the urethra is farther apart in males than in females, as common sense would dictate.
At sexing at this stage, I find it's best to scruff their neck like you would a cat or puppy. The genitalia don't get stretched out of kilter and sometimes when you pick up a male mouse of any age, he'll withdraw his testicles back within his body and make it darn hard to tell. So that could have been your problem when you first got the parents.
I've got some babies like I was talking about the right age to sex. I'll try and get pics up here in a little bit to better illustrate what I'm talkin bout. =P
Here are the pics:
First one is the male. Notice the larger penile area, and the gap between the rear and penis.
Here is the female. Notice the developing nipples showing, and the closer proximity of the urethra and rear.
I just chose black cause it's really easy to see the color difference. White, you can still tell, but you have really notice the hairlessness around the nipples.
The male was squirming a lot, and I didn't get a pic of what I was wanting to show for his genitalia, but the little female was obviously sleepy and relaxed when I picked her up.
I hope that helps you some. But I usually sex by the presence of nipples, and then double check using the genitalia.