Free up some space friends, apparently this package is at a minimum 700+mb download and we all know how apple handles updates to anything app store, same applies here. Will likely need at least double that during the install process to complete. Also, battery plugged in shouldn't be to much of an issue for us, my ipad lost about 7% total battery during the entire process.
Hit settings, general, update button and go get something to eat, takes 30 minutes to an hour depending on your device. Oh and once thats done get ready for a flood of app updates for all your games...
In all honesty I like iOS updates for that reason. I watch my games... of which I have entirely too many and the ones that don't receive an ios update after say... 45 days I consider to be dead and usually uninstall to make room for more games.