The auction website says Monday that Richard and Mayumi Heene (HEE'-nee) are extending the auction until Friday.
The Heenes announced the auction June 1 and suggested a bid of $1 million. Their attorney says all proceeds would benefit earthquake and tsunami recovery in Japan.
The delay was reported in The Coloradoan.
Authorities chased the UFO-shaped balloon in October 2009 but the 6-year-old boy wasn't inside. He was later found at home and authorities accused the Heenes of staging a hoax to promote possible reality TV shows.
Both parents served time in jail and the family later moved to Bradenton, Fla.
