we have our first semi-longhair DLH...while my daughter still in my beloved wife tummy!
..then after she about 1-2 years old we started to add more longhairs...such as Norwegian and Maine Coon...
I don't see any problem...as far as my childrens health is concern...they is in excellence health...hardy get sick..ofcourse,
1. You need to make sure the air flows in the house is good (aircond+air filter is suggested but not a MUST)
2. Clean the cat litter daily...in my case every morning before going to work and after get back home..usually if I see a lots of fur...I will vacuum as well.
3. make sure your cat health is in tip-top condition by checking them monthly with vet (if outdoor).
Overall cleanness plays important part.
THE DO AND DON'T
1. Make sure your cat nails trimmed always to avoid them from hurting your baby just in case.
2. Teach your children not to puke the cats or even pick them up...unless they are about 7 years old which they can know whtr the cat is in upset mood. Use 'mice on the rod' for playing.
3. Always comb your cat to take out the 'dead hair'
If you have baby, don't worry if your cat temperament is good they will never act dangerous to your baby...my cats even sleep near my baby.
Goodluck!