I suggest you transfer the data using the old ID on the phones and then switch to the new ID. When changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. If possible, also set up Family Sharing between the IDs to keep access to your apps/purchases.
How to switch Apple IDs on your iPhone or iPad.
How to transfer all files from one iCloud account to another.
What to do after you change your Apple ID or password - Apple Support.
Family Sharing.
Family Sharing - Set up.
Transfer content from an iPhone, iPad, or iPod touch to a new device. *
https://www.youtube.com/watch?v=kb7u-N_rFE4
Quick Start to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch. *
Use iCloud to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch *
Set up your iPhone, iPad, or iPod touch - Apple Support. *
https://www.youtube.com/watch?v=3rHtV3ZDdgQ&list=PLIl2EzNYri0fwwkKJtNNX2CksbIqfUuql&index=2