18th Birthday - Question

[Sundae]

I know very little about my nephew, who will be 18 in December.
My Mum never sees him (he's never even been to their new flat, but to be honest, I think in the last year and a half it was up to his parents to drag him... IMHO). And my sister has always favoured my niece - except for the old you-know, tricky time - so is not even being helpful to Mum.

Oh, like Christmas, my budget means I have to plan well in advance.
Tcha, who has children three years apart, so the family have a 21st and an 18th in the same year? I ask you? Although that is a comedy eye-roll, which I would do even if they were the children of someone who loved me.

I've decided on cold hard cash for Samuel.
No-one seems to know him well enough for me to get something very personal, and he will at least appreciate that.

The choices I've settled on are thus:

Currency laid out in a circle, like a pizza, in an (unused!) pizza box. I can sweet-talk one of the independents out of a pizza box. Especially if I offer to buy a real pizza and ask for another box
It will have to be in $, as our smallest currency note is £5 (approx $7.75). I can't afford enough of those to make a pizza style arrangement! But it's easily exchanged.

OR

Fold a British note origami style into a shirt, which I've seen plenty of times and loved.
I'd practice, practice, practice on normal paper before attempting on currency.

I'd incur postage on the pizza box, but with enough time to save I could easily handle that, as weight costs more than size when you get to "small Package" charges.

Which of the above do you think is most cool/ would you get an 18 year old you didn't know/ would impress you as a parent?
He gets the £ anyway, in a special way, not tucked into a card.

Am not really asking for any other options, because my response would be likely, "I don't know if he's into that."
But do feel free if you know of something cool.

ETA - 18 is a major landmark birthday here, although laws have changed since I was 18, so that 16 and 21 seem more significant legally now.
But you are still generally considered to become an adult at 18 still - it's the top rating for films for example.