Setting up my 13yo son’s financial future with gifts from my father.

TLDR: Please see the questions in bold further down! Thanks in advance for any useful information!

My father (in the UK) has more in his pension pot than he feels he will ever possibly need (lucky him!). To avoid paying UK inheritance tax, he wants to give me a fairly large sum of money at some point in the near future (lucky me!).

I'll worry about the majority of the money next year, but for now I want to take advantage of the gift tax free allowances for 2025 before this year ends. As I am also looking to be well set for retirement, I want to ask my father to gift some of that money to my 13 year old son, rather than to me.

Having been through some complicated tax business over the last year, I feel I have a pretty good handle on how gift & inheritance taxes work. But an earlier post here has me a little concerned regarding the intricacies of setting up a bank account for my son.

What I want to do is:

Set up a bank (or Yuucho) account for my son and have him recieve ¥1.1m from his grandfather in both Dec 2025 & Jan 2026.

My questions are about technical ownership of bank accounts, and the mechanics of the transfer itself. I have read that while it will be possible to open a bank account in my son's name, the parent that open's the account still has technical control of the account until the cild reaches a certain age. And further, that this can have gift tax implications:

1. If I open a bank account in my son's name, would any cash gifts recieved into that account actually be classed as gifts to me? (this is something I think read in an older thread).
2. If I had my wife open the account for my son, would that mean the account has nothing to do with me? And thus both my son & I could recieve ¥1.1m tax free gifts per year from my father?
3. Regarding the actual transfer itself, is it okay to just have my father send me ¥2.2m via WISE and then pay ¥1.1m of it into my son's account? (As long as pay it into my son's account reasonably soon, that wouldn't count as the whole ¥2.2m being gifted me, right?)

Finally, I read elsewhere that it is also possible to set up securities accounts for minors. I believe you have to be over 18 to use NISA (as there is currently no Junior NISA). But:

1. Could I still link my son's new bank account to a securities account, and have him invest in a regular 特定口座 ?
2. He could sell the contents (paying gains tax, ofc) and transfer it to a NISA account when he turns 18 (or if Junior NISA was brought back)?

(FWIW, I'll be filling my personal NISA allowance in the next couple of years, so there is no advantage to investing money intended for my son in my own NISA. I'd rather it be seen as 'his money' for tax puroses as soon as possible).