You cannot delete an app once it is tied to your ID
If you do not use the download function very often
Settings - General - Restrictions - downloading apps Toggle to ON (Green)
The app store app will disappear and downloading apps or updating them is not possible without your consent (restrictions password)
But kids almost always find a way - so please also consider talking to the child - NOT for a moment telling you how to parent - but just recapping what we have seen on the forums over the years
There is one caution - the restrictions password cannot be "recovered" if lost - one has to erase the phone and start over - cannot even restore backup
So if you do go with the suggestion - make sure it is somewhere you can get to it if needed or forgotten
Use Restrictions on your Mac or PC - Apple Support