How much sex is too little/too much!!

My SO is has to be sexually active regularly. Ive asked him how often does he expect it and he says " not often " I think he's just trying to be politically correct because we had sex on Saturday today is Monday and we actually got into argument because he feels as though we don't have sex enough and he says it's not satisfying because the kids always interrupt. We have ben have sex since we met, I have done things for him that I have never done before. I dont know how much more he wants. I don't know what else to do. Im 36 and he's 29.