I don't know about what's on nowadays, but TV Cultura used to have some good kid shows, like Mundo da Lua and Rá-Tim-Bum, and they also have Roda Viva, some good shows about culture and documentaries worth watching. I never was one to watch Globo, but they did make some interesting things like Comédia da Vida Privada and A Vida Como Ela É.
It is mostly crap, but you can find some gems here and there (or that used to be the case, anyway)