What do you mean you're "looking to accumulate some sort of interest during that period?" If you're thinking of a bank-like scenario, that's something not advisable as it means you will entrust your funds to a custodian. It's risky and not worth it. The best way is to have your funds kept in a cold wallet. Forget about interest. It could mean your children might not be able to enjoy it.

A hardware wallet is a good choice. Create an address for each one of your children. You can even name those addresses with their names. Give them the private keys as soon as they reach 18. Keep the seed phrase safe and offline all the time. You're saving for your children.

Also, since this is for the next 6-10 years, you might want to focus only on Bitcoin. Avoid altcoins as it could mean they're already worthless by the time they're given to your children.