Hi again DennyMo,
The jumper modification is only semi-permanent and you can swap back to 5V whenever you would like but it is a bit of a hassle since you would need to get out your soldering iron each time you wanted to go between 5V and 3.3V. The spacing of the jumper pads is too small for that header, unfortunately. You could remove the header pins from the housing and manually place them but that might be more hassle than it is worth and then you're stuck with trying to find a jumper small enough to fit on those pins.
If you do not want to modify the jumper, the next best option outside of getting a 3.3V FTDI would be to level shift the serial pins on the 5V FTDI down to 3.3V. You can either use a Logic-level shifter
or you could create a voltage divider
if you have some resistors available. There is a calculator in that tutorial I linked that can help you find the right values to go from 5V to 3.3V.
Finally, you can use VIN to power the Papa Soundie with 5V but you will still need to shift the serial signals down to 3.3V to upload to the board. Connecting 5V logic to the serial header will most likely not immediately damage the ATMega328 but continuous use will eventually cause some damage to it and the board will no longer function properly.