Remove trusted device for 2FA but not from iCloud?

How do I remove devices from the trusted devices list so they aren't the ones asked for 2FA prompts, while still keeping them linked to my iCloud account? I have an old iPhone just used for taking pictures, and an old iPad that gets used for "cat TV" and showing people photos on a larger screen. They never leave the house and I'm sick of being asked to use them to authorize things on my phone when I'm not home. I still want photos to be able to sync with my iCloud account and be able to download apps on both devices.