Well, instead of completely deleting the player, you can temporarly disable the CharacterBody2D and then do animations/other stuff in your children.
When they die, You can set player’s CharacterBody2D disable_mode to DISABLE_MODE_REMOVE and process_mode to PROCESS_MODE_DISABLED, that way the character’s _process functions will no longer be processed and their physical collision not be used.
To still make sure your children are being processed, you can set their process_mode to PROCESS_MODE_PAUSABLE
You can send out death signal to children if you need to send them an event
I recommend you follow the official 2D Tutorial. These are all basic skills. The tutorial will teach you how to do everything you asked about and teach you how to use the engine.