Eshop code from Amazon Japan is quite cheap compared to buying locally.
I think the process for this would be moving my account over to Japan, which would also move his, redeeming the eshop code on his account , then switching region back to our local one.
Have I understood that correctly?
If you are getting game code, instead of gift cards, then this should be fine. It would still be better to have a separate JP account for logistics though, or in case Nintendo changes something in the future.
For gift cards, oji has explained the issue below. You get card for $10 and the game is of $9.99 so you are left with $0.01 and then can’t change your region.
Really the bit people seem to be missing the mark on, is whether or not my changing the region on my account will also pull my children across with me and in turn let me redeem the code on my sons account.
From research, I think it will but just really looking for confirmation.
No idea about that, but same rules apply, so if you both have 0 balance, try changing and the account and see. Worse case scenario you will have to change region for two accounts instead of one.