JISAs for both of ours. They are building an awareness of investments via our Vanguard friends mostly, but also one or two other tracker funds.
They also have current accounts, but they are teens. Always saving half!
The only pain with the JISAs is how to pay money in. When they have a lump sum saved (say £200) in their own account, they can’t pay it in themselves - they’re not over 18. So we have a protracted game of ‘move the money’ - birthday cheques in to their account, transferred to my account, then into the JISA. And it is characterised as a gift from me (which it isn’t). I’m banking on the clear audit trail showing the transfers being enough to show the provenance of the money if I need to.
The wonders ...