I don't work in the rescue 'sector' so maybe my opinions aren't as valid as those who do and have had more experience in this type of thing . . . but I think that (if you have the time) each request should be taken on an individual basis and assessed on its own merits, rather than having a blanket 'ban' on kittens/young cats going to a household with a new baby/toddlers.
Personally speaking, cats came first into my life. When I had my daughter, her needs were attended to but my 'first borns of the furry variety' still came first
Seriously though - not all people who have children suddenly abandon or neglect their cats. Of course, I go to rescue shelters and I see the 'new baby' reason given for why the poor cat is needing a new home and I just can't understand it. The only time I suppose it makes sense is when the cat is stressed out by the new baby - but from a responsible cat owner point of view, steps can be taken to ensure that the cat doesn't get to the point of being that stressed!
If the people who are requesting a kitten from you are on their 2nd or 3rd child then they probably have a handle on the whole new baby thing. I think we've all seen people juggle a lot more! And again, from experience, if good behaviour around the cat is modelled then the child pickes this up - my daughter NEVER ONCE picked up or pulled around our cats as she was growing up - and even now (aged 6) she knows that she doesn't pick them up. They have a great relationship with one another (see side pic!) and waits for a cat to come to her to sit with/on her, not the other way around. It's all about setting a good 'training.'
If a kitten is homed at about 3 months (is that right? I've never had a kitten before) and the potential owner is still pregnant, then the cat may well be just over a year old before potential baby-pulling. (If you know what I mean . . .) Plenty of time for 'training' on all sides!
Ultimately, I suppose I would look at the family, their cat owning experience and the behaviour around cats of their existing children. Then you might be able to get the measure of them. Part of me thinks that if they don't get a kitten from you and are set on getting one, they'll go to the free-ads in the local paper and get one regardless - and I'm not keen on perpetuating the supply/demand of back garden breeders. At least you will be able to offer them advice . . . . . . .