Quite surprised to hear of the breeder suggesting that you may have 'problems' with a Red and children
The Cocker Rage thing is very very rare and if you search on here you will find many threads explaining it all. I have a Red male and I have to say in all honesty that he is the gentlest soul, I also have a solid black female who is also an absolute sweety, they are by nature very loveable dogs. I am going to give your breeder the benefit of the doubt and suggest that it was the age of your children that was causing them concern.
I have 2 cockers Belle who is nearly 3 and Monty who is 2 and I have 5 children aged from 13 mths to 15yrs so I am not against pups and children but 4 mths is very young to introduce a pup into the mix, mainly because the pup will be soo demanding of your time
It can be quite stressfull owning a new pup , add that in with looking after a new baby and managing training the pup and your 6 yr old, pups tend to playbite a fair bit especially their little humans.
Please don't think that I am anti dogs and children , nothing could be further from the truth but because of the difficulties I have explained above you may have trouble finding a good breeder that will sell one of their pups to a household with such a young baby.
When we got Belle my youngest was 3 and her breeder was very dubious about selling her and it took a lot to convince her that the kids were responsible enough, we had just lost our 10 yr old cavie so they were used to canine company
I was just pregnant with my youngest when we got Monty, if I had known then that I was pregnant I would have postponed getting a pup in all honesty.Good luck with whatever you decide