One question I've got is what size iPad to use?
I notice that the OzRunways people seem to recommend the iPad mini, but the mini screen size appears to be smaller than the A5 size for an EFB specified by CASA.
Regarding power, the easiest approach is to fit an automotive-style cigarette lighter style socket to the panel of your plane. A company in the USA even makes a cigarette lighter style socket that has TSO documentation.
On eBay you can buy a cigarette lighter plug has has one or two USB sockets on it. Most of these USB plugs will convert the 12 or 24 volts from the plane to 5 volts for USB.