I will move the 3.3v and GND for the TMP117 to the Due.
Everything powers up at the same time, with the power on button, I don't know if something power's up faster than other devices though.
I have a couple different power supplies. I have a 48V to power stepper motors and a 12V to power cooling fans for my enclosure. I was going to power the Due from the 12V supply and was told that was a bad idea as it will make the Due overheat trying to dissipate the heat from the extra voltage so I bought a buck converter that had 4 different voltages to choose from.
I was also told I shouldn't really power anything from the Due and since I had multiple voltage sources with the buck converter I power all devices from it.( the buck convert has 3.3V, 5V, 9V and a variable voltage on it)
I have six steppers, 2 cooling fans, 3 proximity sensors, 2 IR sensors, 7" TFT screen and the TMP117 to power up so I was trying to limit the amount of work the Due had to do.
I know all the sensors have GND on them but I don't know anything other than how each respective devices wiring diagram wants it to be hooked up.
Thanks for the help.