I'm in similar situation Safyno, only with one kid and she's more involved with religious functions. Just try to do things mentioned here. My s.o is very perceptive so my subtle attempts to bring up the subject failed miserably.
I dunno, it could be having a little one is overriding her sexual desires. We use to fuck like crazy now she just has sex once per evening when we do and sometimes she don't even want to get off. I dont want to come off as a ass. I love my child and wife its just frustrating sometimes.