Hey John, Best way to check what your kids could ride would be through Disneysea's official website (click under "TDS attractions") which states clearly which rides "do not have height restrictions". You could also select the "above 90cm okay to ride" option if you've a 3yo who's above 90cm. Looking through that list - you'll get a rough idea what your kids can and wanna ride. 20,000 Leagues' submarine capsule sits six. Two facing the front, four facing the sides. Trust me, you'll see more on the sides. Our family of four took the front and inner side and even switched seats quietly during the ride because of the fussy little one - it's actually very slow and safe. HOWEVER, it is dark inside the capsule and they made the illusion of the submarine going underwater with some "sea monsters" that made my 5yo really scared even on the second time we took it. Might wanna mentally prep your kids before going on the ride! Yes, all shows by lottery only. Big Band Beats was just the most entertaining show that's why it was always mentioned by most influencers. HOWEVER, all first shows of the day can be entered by queuing (without the need to win any lotteries). If you're there before most people i.e. say at least half an hour before the first show starts, then yes, it is possible to queuein about half an hour. If you go during off-peak days. Have fun!

We used Klook and it worked fine. I think everyone has trouble buying tickets from outside the country. You could also try the Tokyo Disney resort app.

I booked mine on get your guide The sale went through easy but the tickets didn’t come I then had to email them and they sent the barcode tickets in an hour or so ( very easy) (Maybe download the app first )

It depends on what you count as convenient, it's about an hour by train to Shinjuku/Shibuya. So long as you account for the commute in your plans, it'll be nice!