Travel with JR Pass

Hi!
If I buy a JR Pass will it include a Bullet train from Kagoshima to Osaka, Osaka to Kyoto & Kyoto to Tokyo?
Will the JR Pass get me around Osaka and Kyoto and Tokyo?
What hours do the trains usually run?
Also I have 2 children under 6. They will be 4 and 5 when we travel. Do we need to buy them JR Passes or are they included? Also if I don't need to buy them a pass, can I still book them a seat? a 5 hour trip seems like a long time to have a 5 year old sit on your lap.

thanks!
Leah