Apple TV /Airplay question

I have a Macbook Air, an iPad mini and an iPhone 4.

I'm thinking of buying an Apple TV, partially because it will be fun for home but allso for doing presentations wirelessly in various companies I visit (rather than having cables all other the place - I like to walk around)

So I know I can create a wireless network on the Air and connect the ATV to that and AIrplay

Can I also connect the ATV to the iPhone's hotspot and present from the iPhone?

Is there any way of connecting the IPad mini to the ATV to present or do I need a separate wifi source?