My son and I presented at brickfair alabama last month. He wanted to display his minecraft and castle MOC's, so I went with your theory, build something big to attract attention and then put the smaller things on the sides.
It worked perfectly, we built an 8ftx 3ft battle of hoth scene which was a crowd puller. People spend more time looking at big scenes and then notice the smaller ones. We are now scaling up Hoth for the next one, planning in 12ftx 5ft :)
Have fun, listen to the advice of making it 'modular' for easy transportation