Hi Greg, my family and I are planning to visit Tadami Line in Fukushima with one night stay. We will reach Haneda Termainal 2 Airport at 12.10pm from New Chitose Airport on 9th Dec 2019. From the airport, I would like to look for the fastest and cheapest way to go to Tokyo Central Station where I can use Tohoku Shinkansen to Koriyama. Due to the time consuming, and not familiar with Haneda airport, would appreciated if you can guide us the best and cheapest way heading to our destination. By the way, please advise will there be more economical to buy the JR East line pass for my trip? On day, we will travel back to Tokyo and stay for another 2 nights, our family is with 2 children of age 8 and 9 years old. Is the Disney Sea World a suitable theme park for them? Thank you in advance on your details information.
I recommend the website www.hyperdia.com to look at train routes. It will tell you both the fastest way and the cheapest way to get somewhere. Another option is using google maps. They do a good job with city bus routes.
I will say that the trains are generally easier to use since there is very little bus info in English, and bus drivers generally only speak very basic English. For example, if you ask “Tokyo station”? they will be able to say yes or no, and that’s about it. The announcements on the bus are only in Japanese, with Japanese characters on the signboards. If I were you, I would only use the bus if a train route is unavailable.
From Haneda Airport to Tokyo station is quite easy. There is a train from the airport called “Haneda Express” and it will take you to Shinagawa. From Shinagawa, there are a couple of options to get to Tokyo station. Price wise it won’t make much difference, both routes cost the same.
The Hyperdia site will also help you compare the cost of travel with buying the JR East pass. I just did a quick check, and it looks like from Tokyo Station to Koriyama costs 8,000 yen one way, with a reserved seat. The JR pass is much more expensive, and I would only recommend you buy it if you plan to take the shinkansen several times, in which case it would pay for itself.
Keep in mind that the age of your children will determine how much their tickets cost. Toddlers are free, and children under 11 are half price adult tickets. That will save you a bit of money. There is a special button on the ticket machine to push when you buy a child’s ticket, and when the child goes through the gate it will make a chirping sound to let the staff know. That way adults can’t cheat, LOL.
As for Disney Sea, it’s great for kids, as is Disney Land. I have heard adults say they find Disney Sea to be more fun, but I personally don’t really find much different between them. To me they are both for kids. 
Thank you very much for your advise and tips given. I feel very grateful and appreciated with the time taken by you to search and check out for me. Once again thank you and have a good day.