[Nyororin]

With the tourist visa, your husband`s visa should have no effect on your own. Regardless of family connection, with the tourist visa you will all be receiving it based on your nationality. If you are not from a country with 6 month tourist visas, you will not be able to receive one even if your husband is.

I do not know the policy on issuing length for those with multiple tourist visa lengths. He may have to come in on 3 months then renew the tourist visa, he may have to show proof of funding in advance to receive the longest, etc.

If he comes to Japan on a cultural activities or student visa, you should be able to receive a dependent visa allowing you and your son to stay in Japan with him for the length of his study.
However, with the cultural activity visa I believe that he will have to be enrolled into some sort of program with them sponsoring him. In the case of Karate, it`s likely that he`ll need to have the dojo set and have contacted them about learning there long term before that route would be open to you.

I`ve never been to Okinawa, so can`t comment on how things are there... But I have heard that the local attitudes toward foreigners tend to be colored by the US military presence.