Spanish at home

I've been trying to speak more Spanish at home, I even put signs all over the house to remind everyone that we should speak in Spanish as much as possible this month. As I mention before we will be visiting my family in July.
My nephews speak a little bit of English since they are learning it in school but it'll be nice if my kids can communicate with them in Spanish.
My oldest one (9) understands everything I say to him, he just refuses to speak it. He's such a perfectionist! If it doesn't come out right the first time he convinces himself he can't do it! Just like his father :).