There is no other screenshot option provided by Apple I presume mainly because a single click option could easily result in lots of unwanted screen shots. I get accidental screenshots all that time when I grab my iPhone with my big hand that easily wraps around it. There are however a number of third party screenshot apps in the App Store and perhaps one of those might suit your need.
Even in background Navigation apps can and will suck power and download bandwidth. How much of each depends on the App and what features are activated.
As far as shutting apps down, I think the finger gestures in the more recent iPhones and iPads that are without home buttons are a LOT more convenient in that regard, albeit a tad bit expensive if that is the only feature you are interested in.
