Graphics projection

Hi,

Hoping someone out there can advise me.
I am putting together a presentation film consisting of shot footage
and animated stills and text. Its being projected onto an area roughly
4x3 metres using video projector.

What size should I make my Comp? Also there is a resolution issue with
some of the still images as they are quite small. Im guessing that slight
pixallation will be less noticeable from a projection as oppose to a screen? There will be a fair distance between the projection and the viewers.

Anyway, hope someone can help!

James