You can create a wallet address for them on a hardware wallet or airgapped device and send Bitcoins regularly to it. You can also intimate your spouse of your plan and teach them how to work around cryptocurrencies if they are not savvy, so they can always access the funds should anything happen to you and still fulfill the purpose.
Of course, the option you suggested is more reliable and better, but you can also get by with the simplest one. Namely, create a wallet in electrum (after taking care not to compromise the key) and keep several copies of the btc address for receiving. Of course, write down the seed-phrase and save it in a safe place, and uninstall electrum wallet and all related files.
To the extent necessary, send money to this btc address and accumulate it there. When the time is right, just give the seed phrase to your child.
Also, I agree with
Upgrade00 that one can't do without teaching the child (at least) the basics of bitcoin. When will he be able to assimilate such information.
I'll be depositing funds in their accounts regularly, which will keep sitting there for about 6-10 years, so I'll be looking to accumulate some sort of interest during that period. What options should I consider for this?
This would require some sort of staking on a centralized platform. This comes with the risks that you are not in control of the funds and the platform can fold, seize or freeze the funds or get hacked.
If you're going to invest in a decentralized asset, you should not shirk the responsibility that comes with safeguarding the assets.
Accumulation of interest on the account will not be necessary, as btc will generate returns far in excess of any interest promised by the centralized platforms. Risk for the sake of meager interest, giving your funds into the wrong hands? What might not be smarter.