The advantage to being five, I think, is that most learning is fun. I mean, B has found a few things hard to learn but even then, he gets help and we try to set him up so it is possible for him to learn.
One of the difficulties B has is that he doesn't have the same vocabulary in his second language as he does in his first. It will always be easier to speak in English. Gaining vocabulary in the majority language is easy too, because everyone speaks it and because the books we read in English are harder than the books we read in Japanese.
So I'm still working on ways to close the gap between the minority language and the majority language. The main problems I'm running up against are: I don't have a lot of vocabulary, (and the vocabulary I do have is more typical of language learners than the kind of things families say at home) and that we don't have a lot of time each day. B is overprogrammed.
What has worked well this weekend is a little game called Neko Atsume. It's an iPad app, and it can be switched from English to Japanese fairly easily. (It's in the settings section of the main menu). It reminds me of a tamagotchi. You use fish to buy food and toys to put in specific spots. Different cats come and play with the food and toys. The cats will leave you more fish. B can't quite read in Japanese but he knows the writing is in Japanese so he will try to discuss the game in Japanese. You can't play for more than a minute or two at a time because nothing much happens, so it brought us back to Japanese several times per day so we could check to see if any cats had come.
In our regular routine, today I read him a Penelope book. He really likes this series of books. Penelope never gets it right on the first try. To be honest, I think if I were reading them in English I might get bored of them because they are a bit repetitive, but because I don't really know Japanese, I appreciate the repetition. It gives me a chance to figure out what it means.