According to http://en.wikipedia.org/wiki/List_of_fatal_alligator_attacks...
There had been a grand total of 4 fatal alligator attacks in the USA in the 1980's. It seems to me that the father probably realized that there wasn't actually much danger involved for his boys.
And I think your proposed scenario
> Would it be equally character-building to make them run across a freeway to find a dropped pair of sunglasses?
is a little disproportionate, risk-wise: http://www-nrd.nhtsa.dot.gov/Pubs/809-456.pdf "Pedestrian fatalities from all crashes reached a low of 4,763 fatalities in 2000"