rasperry pi with i2c arduino leonardo
Yes, there is a safe and simple way to proceed.

The Arduino can be powered from a +5V source (connected to the 5V) pin. The schematic allows for both 5V from the Arduino's voltage regulator or 5V from an external source (like from USB) with protection for the LDO. So you can supply unregulated power to the RaspberryPi and use it's regulated 5V to power the Arduino.

If doing this, I'd suggest powering the RaspberryPi with a source > 5V. From what I've seen the RaspberryPi's voltage regulator can supply up to 1A of current. This will be shared between the RaspberryPi and the Arduino. So, you'd need to keep an eye on your design to ensure the overall current consumption stays below 1A.