Hi!! I agree with Sakamoto san. First of all, please check that the restaurant is non smoking or not. As I had an experience, the essayist way to find the family friendly restaurant is to go to department store or shopping mall. They clearly mention which restaurant is non-smoking or baby welcome. There are kind of izakaya/fine style restaurants as we can find all traditional Japanese foods!
Hello,Most of restaurants are badys welcome,but some of restaurants are not bady welcome,in Japan still can smoke cigarettes inside of restaurants,some restaurants are separately,smoking seats or non smoking seats,but small restaurants are not separate smoking or non smoking seats,should be ask restaurants stuff about that before go or make reservation for restaurant.