Originally Posted by
AlwaysAisle
Possible situation will be the chance of all your traveling group not able to sit together. Green car is reserved seat with seat assignment at the time of ticket is issued. Using JR pass means you will not able to reserve the JR ticket till you arrive at Japan, which is likely starting date of your trip. I think getting 10 seats together may become little difficult.
For purchasing regular JR tickets, tickets are sold from one month before the date. However, for group travel of 8 or more get 10% or more discount (depends on number of people in a group) and accepts reservation (actual ticket issue is from one months before the travel) from 9 months in advance, such will assure that group will get seats together.
You do get free reservations with a JR Pass, and since the Shinkansen trains run so frequently, you should be able to find a train with open seats in the desired configuration unless you are traveling during a peak season.
One thing you will notice is that Japanese crowds tend to be quieter than crowds in many other countries. You will want to caution your children to use their "inside voices" at all times in Japan.