I'm really touched by the video! Will make an attempt to translate the first part of the video... the lyrics are too tough for me, maybe someone else can try? haha.
Here goes:
Hello! Imai Eriko here. I'm finally back! Today is 24 Jan and I am at the Tokyo Education Board Symposium. I announced this news on my blog as well - I'm going to sing a song called Yurikago (means cradle) today. See you!
Host: Let's put our hands together to welcome Imai Eriko! Wow, such a enthusiastic response!
Host: What has been your happiest moment recently?
Eriko: My happiest moment recently is when my son, whenever I bring him out to play and he finishes playing, or when we complete doing something, he would sign to me and say 'mama, i enjoyed myself.' That makes me very happy. I have been having difficulty understanding what my son says for about 3 years.. so now that I can understand him, I feel very happy. Recently, we went to the planetarium, (whole chunk I can't understand here, but something about Eriko not really liking the planetarium), after that, my son signed 'mama, I really enjoyed myself today'. These simple things that make me happy.
Host: Imai, what are your dreams for the future?
Eriko: For me, being a singer, I hope that my songs can reach many children and make them feel that music is wonderful and singing is enjoyable. As a mother.. I told the story of my son over the 24hours TV program, but as my son is still young, he is not able to tell me 'mama, it's great that so many people have seen our story.' I hope that he will be able to appreciate that next time.
Eriko: Ok, now.. (turns around and tells the students behind her to step forward abit) I hope that this song can reach the hearts of all the children in Japan and all the children in the world. I hope everyone can sing along. This song is called 'Cradle'.
Song starts. Eriko breaks down about 3/4 way through the song and stops singing but continues to sign. She managed to recover and sang the last part of the song though!

Hope someone can translate the lyrics! ;)