You should probably go through your pediatrician, and then go through the pediatrician for a referral to an allergist. Unless you think your pediatrician is doing a terrible job, they are pretty well able to handle mild allergies--but if you suspect other things besides the cats or if doing the things below don't help, then allergy testing is the better way to go, and a referral from your pediatrician will get you in much faster than you just calling up an allergist on your own, usually.
Keep the cats out the bedroom, and preferably out of the main area she plays is every day, if possble. If she has contact with the cats or the cats' area a lot during the day, make sure to bathe her at night before bed, including washing her hair, and make sure to try to keep on top of the cat hair (I know, I know, it's a neverending struggle against pet hair, LOL).
You can also talk to your cats vet about options. Bathing the cats more often (say, once per week) may help, and there may be other options available. The majority of people who are allergic to cats are allergic to an enzyme (aka a protein) in the cat's saliva and/or the dander; since cats lick themselves all over, pretty much all the hair will be causing problems to someone who is allergic.
Also, another poster said that the cats will make your child asthmatic. You might want to read up on it a little bit before you get rid of your cats. Here is an article that may be of interest:
http://www.webmd.com/asthma/news/20070928/cat-allergy-lin...