you could point out that traffic accidents are the leading cause of death in young people and young adults (likely injuries too)

Obesity is a leading cause of morbidity and death amongst older adults.

You could suggest that by rejecting wal-mart the local kids will be less likely to be killed in car accidents, and their parents will have a lower incidence of disease (living in an urban/walkable neighbourhood is correlated with 6.3 lbs lower average body weight). Because they will be living in a more walkable neighbourhood.