How to send any kind of voice messages from phone to a tablet used by a kid who can't read? My daughter is  4 years old and she can't read. She is using an Android tablet for games and YouTube while I am away. 

I am looking for a solution to send her voice messages from my phone. Any kind of voice messages would be great (voice, prerecorded messages, TTS, and more). It should be played instantly, whatever activity she has currently engaged into on the tablet.

How can I do that?
Depending on how those messages should reach the device, and based on what event they should "pop up", this could be accomplished e.g. using tasker. Tasker is the most potent automation app for Android, and a.o. can utilize TTS to read text, but also can play sound files. It can react on a multitude of events such as time and location – but also on more device-specific events like battery low or a changed network state (see e.g. my list of Tasker resources for more details (and also howtos/tutorials) – especially watch out for the graphs in the lower third of that page for available events and actions). So you could e.g.:


play a certain sound-file each day on 12:00 am (optionally: only when the screen is on, i.e. your daughter is actively using the device)
read the content of a text file whenever that file was updated (useful in connection with some other app/service transferring that file to the device, e.g. using Dropbox or FolderSync)
use TTS or a pre-recorded sound file to be played when she leaves a specified "safe area" (see: Geo-Fence), or when she opens a certain app
and more


Of course you could also install some VoIP app and ring her tablet so she can pick up the (video-) call for interactive messages :)