Obon 2015 is jr pass green worth it?

Hi,
We will be traveling during obon 2015 with 3 kids and need suggestion I whether or not jr pass green will help us together a seat on Shinkansen

Below is our itinerary
August11, Arrive Narita. 3.15pm
August 11, Narita express to Tokyo station
August 11, Tokyo-Kyoto Shinkansen , green car ??
August 13, Kyoto-Tokyo
August 13, Tokyo disney sea and other travel around Tokyo
August 15, leaving Tokyo

I am worried since we arrived on the 11th late afternoon and the same day we will try to
Go to Kyoto.. Is it better to just buy regular jr and wait in the unreserved train ? Or if we green car pass and can not make same day reservation what would happen, we would have to do unreserved train anyway right ?
How about going back Kyoto-Tokyo on the 13th I was hoping I can already make reaervation for this once we landed in Tokyo....

Or is it better to just buy Individual round trip Shinkansen and then reserve seat with travel agent prior to our arrival in Tokyo ? In that case it will be regular train, not green.. And then buy other passes for our inside Tokyo trip and Kyoto trip, if so which pass would you recommend ?

If we got regular jr pass and there is seat I green car can we upgrade to reserve ? I have heard that it is very expensive that way specially if we are doing it for round trip Tokyo kyoto... But that way we could just do regular cars if we can not reserve train..

Pls advise, thanks in advance...

You can reserve tickets with a regular JR pass, you will be seated in the reserved carriages rather than the green carriages. The green carriages are just a higher class on the train.

When you arrive at Narita, change your exchange order for a JR pass and book the shinkansen tickets there at the same time as booking your Narita Express ticket. It's better to go from Shinagawa station to Kyoto rather than Tokyo to Kyoto, the transfer at Shinagawa station is much shorter and more straight forward. (the N'EX stops at Shinagawa before Tokyo, so you don't need to worry about taking different trains) You can also organise your return ticket to Tokyo at the same time if you wish.

Thanks for the suggestion. does Shinagawa station have same frequency of Shinkansen to Kyoto as Tokyo station ?
How long will the queue be if I could not reserve a seat ? Will it be more than 30 min ?
So green pass does not really have advantage since most green will be sold out anyway ?
Thanks..

The NEX goes from Narita to TOKYO, then to SHINAGAWA.
Shinkansens start at TOKYO then stop at SHINAGAWA.
Obon is August 13 to 15.

How old are your kids? This could make a big difference to your thoughts since kids under 6 can travel free in unreserved.

See the relevant pages on the main Japan guide website for all the info you need on that.

Disregarding the thing about kids' ages, you could save yourself 50% and just get regular passes; you're basically just taking a chance as to whether you get reservations and the green pass option costs you 50% extra if you all need passes and a heck of a lot more if you have kids under 6.

My kids are 5,8 and 10
We don't plan to buy pass for the 5yr old since we think it's hard enough to get 4 seats.
Seems like green pass is useless if it is sold out ? Given we are arriving in narita at 3pm and plan to take the Shinkansen on the same day ? Will we even get a chance to get in the train that day ? How long you think will the wait be .. We are traveling on August 11 Tokyo kyoto. And then going back Kyoto Tokyo on August 13th..

The 11th will probably be OK to get seats. The 13th will likely be crowded, but if you get your seat reservations on the 11th when you get the pass you ought to be OK. You will need to specify the time.
The Shinkansen seats are 3 across on the left side and 2 across on the right side going to Kyoto. From Kyoto to Tokyo they will be 2 on the left and 3 on the right. The 3 across are A,B & C. The 2 across are D & E. You can specify when you reserve. D&E are on the side to see Mt. Fuji as you pass, if it's clear weather.
Also, if you get, for example, 8 D&E and 9 D&E, maybe you can turn the seats to face each other. I've never needed to do it.
And maybe the 5-yr old can squeeze in someplace.

Thanks,
I will define ask for d, e seats back to back if there is any and yes my 5 yr old can be just between us..
Cross my finger I will be able to board to Kyoto soon enough that day..

"Cross my finger I will be able to board to Kyoto soon enough that day.. "
I don't understand what you mean. With reserved seats you don't need to worry.
You want to change at SHINAGAWA, not TOKYO. The train stops at SHINAGAWA for only 1 or 2 minutes. Your ticket will say which car number and the platforms are marked . Just stand at the right place and you can get in right away.
When you get out of the NEX at SHINAGAWA, go up the escalator and it is just a short distance to the Shinkansen gate. It is well signed in English.

At SHINAGAWA you will have a few minutes to spare. I suggest buying a Bento (box lunch) to eat on the train. They will be on display at the small shops on the platform. If you don't know what you want ask for Tori Bento (Chicken Bento).