Divide the groups in two based on familial affiliation (they'll expect that).

Ask the following questions:

1. My radius of "personal space" is... (tiny/small/medium/large/immense)
2. I am... (short/somewhat short/average/somewhat tall/tall)

Bias x by (1) [near aisle should be "tiny"] and y by (2) [back should be "tall"]. Average groups, ignore children.