P/S for Arduino + Adafruit NFC + WAV Shields + PC USB Amplified Speakers

Hi everyone!

First post and probably not the last. I haven’t dabbled in electronics much since the Navy but because my son has been hounding me to build THIS, I think it’s time to start designing/building it the way that will work best for him.

Quick summary: System consists of one Arduino UNO Rev3, Adafruit NFC and WAV shields. We are building an acrylic enclosure that will also house two small 3” computer desktop speakers (amplified versions that pull 5VDC power from USB port and then 1/8” stereo jack).

I want to power this setup most efficiently and from reading the power requirements found from Tech Specs HERE Where it states: “The board can operate on an external supply from 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.”

So please advise if my power plan below is best suited for this project:

Using a 9VDC 1A wall-wart (2.1mm plug center pin +) to power the Arduino and Shields mentioned. Then, tap off Arduino pins 8 and 6or7 (Vin 5VDC and ground) for the small speaker CKT (speakers draw max 3W).

If my power supply is powerful enough, then would this be the best approach for this setup? Else, what would you do?

Thank you,