This year we opened the boys a bank account each. We transfer money each week into their accounts. $1 for each year (DS#1 is 11 so he gets $11 a week, soon he will get $12 a week etc) of their age.

It is just a kids account at one of the major banks. They don't have any account fees and get ok interest (nothing huge)

At this stage we are happy with that. It can't be taken out unless we go into the bank.
They should each have about $15,000 by the time we give it to them. We will make up DS#1 and DS#2's balance to equal DS#3's balance due to starting his many years earlier.

Good luck with your decision !