Q: iOS update to 9.3

Restart the device, check you have a strong wi-fi signal and a well charged battery, or put it on charge, then try again.

tt2

There are many reports about the servers being overloaded. You could wait a bit and see if it comes across or perhaps try updating through iTunes - server issues may affect you there also.

If "Activation" is in fact the issue - NEW article as of TODAY => If you can't activate your iPhone, iPad, or iPod touch after installing a software update - Apple Support

Apple has apparently pulled the update for older devices.

http://www.imore.com/apple-working-ios-93-fix-older-iphone-ipad

Glad that it worked through the MBP....   

too little, too late, I fear

You are right...  but maybe the articles linked above will help others.