Your second drawing ( I really don't like fitz 'drawings' compaired to real schematics, even hand drawn ) is pretty close. You should look up 7805 regulator circuits and see the input and output capacitiors they require/recommend. Also while your IR sensor will work as drawn, you can optionally also wire just the sensor's red wire (+5vdc power) to the Arduino +5vdc pin as that sensor only requires about 33ma or so. It's the servo that can require high current and thus requires an external voltage source like your battery pack.