WiFi tether without losing battery
It is hard enough to keep it charged with the GPS and streaming - I know I do it frequently. I would not recommend trying to share data at the same time. It wasn't until the latest update that I could even get streaming and WiFi hotspot to work without stuttering.

I would strongly suggest that you use another cell phone do the WiFi hotspot while your phone does the streaming and GPS or get a dedicated GPS and use the phone for hotspot and streaming.

It is a classic example of GPS, BT &amp; Wifi Hotspot, Pick any two. 

But, in the interest of science, I think you should try it ;) just have a backup plan.

Edit: Be sure to get a high amperage car charger - one for an iPad should work nicely since those require 2.1 amps. That should push a lot of juice to the phone and maybe keep it from dying under all that load.