sounds like a neat project!
you might still consider the mini LED projector... if you used one with some transparent holographic projection film (like this: http://www.ugo-media.eu/materials/ho...lm/clear-film/), it could be pretty impressive.
what size do you think the viewable area will need to be? i think you could get around the projector distance issue... most of the portable projectors have pretty major zoom, like the PK301 (which would be overkill probably at 300 lumen) will produce a 5" diagonal screen at only 7" away. i know there are ones that are even better for short distance projection.
just some ideas