Is it possible to make it so a user can use the sudo command in terminal, but not have access to sites other then those allowed through parental controls, without a third party system?
By adjusting the sudoers file (/etc/sudoers) with
sudo visudo it should be possible to accomplish this. It is a hell of a job and you need a profound knowledge of all commands to fine-tune this while avoiding errors and loopholes though.
You have to add the user to the User privilege specification section
... # User privilege specification root ALL=(ALL) ALL %admin ALL=(ALL) ALL ...
Then use a whitelist (or a blacklist) of allowed (or disallowed) commands:
# User privilege specification root ALL=(ALL) ALL %admin ALL=(ALL) ALL user ALL=/usr/bin/nano,/usr/bin/opensnoop
# User privilege specification root ALL=(ALL) ALL %admin ALL=(ALL) ALL user ALL=!/usr/libexec/PlistBuddy,!/usr/bin/passwd,!/usr/sbin/*
You may mix whitelist and blacklist.
man sudoers how to simplify things or narrow things down by configuring User, Runas, Host and Cmnd alias specifications.
Check the accepted answer to the question How to prevent sudo users from running specific commands? for the pitfalls of configuring a simple command like
rnano in the sudoers file.