I'm making a script that will be a double clickable .command file and I need it to prompt for the users admin password.

So far I have:

if [[ "$(/usr/bin/whoami)" != "root" ]]; then 
    sudo -p "Please enter your admin password: " date 2>/dev/null 1>&2
        if [ ! $? = 0 ]; then 
            echo "You entered an invalid password or you are not an admin/sudoer user. Script aborted."
            exit 1
        fi
fi

the way your script is written is to only run the date comand with sudo. if you want to run other commands you should probably create a second script and call that instead of date.

Try this code:

sudo -p "Please enter you admin password: " whoami 1>/dev/null && {sudo whoami;sudo whoami;whoami;sudo -k}