I was not satisfied with either US eyes or a Ledmatrix.
With some -rather rough- modifications I was able to position the 16x8 Led matrix as a mouth underneath the eyes.

I studied ways to have US sensor, buzzer, pushbutton and ledmatrix and I found as the best way this wiring:  

A0 = Pushbutton (switches to +)
 D0 = GPIO16            US Echo pin
 D1 = GPIO4 SCL (I2C)
 D2 = GPIO5 SCA (I2C)
 D3 = GPIO0 Right Foot
 D4 = GPIO2 Right Leg
 D5 = GPIO14 US Trigger pin
 D6 = GPIO12 Buzzer pin
 D7 = GPIO13 Left Foot
 D8 = GPIO15 Left Leg
 RX = GPIO3 // can act as a buzzerpin but prevents uploading.
 TX = GPIO1 // can act as a buzzerpin but prevents uploading.

Some points of concern:
- I replaced the 9V battery cap with a thinner one.
- The pushbotton can be read with an analogRead.
- For the  US sensor the NewPingESP8266.h library must be present.
- I did not succeed in running the Ledmatrix with the sample files but I succeeded with: myLedmatrix.drawBitmap(0, 0, happy, 16, 8, LED_ON); with happy a 'readable' bitmapfile.

Next step will be to implement rolling, walking and remote control.