Christopher Morgan, 47, was sitting alongside his son, Timothy, who was killed when the ride car ploughed into a loose lighting gantry which toppled into its path.
Mr Morgan suffered fractured ribs and his older son David, 15, and a family friend Dominic Evans, 12, were also injured.
At Cardiff Crown Court, a businessman, Pat Evans, 73, admitted failing to carry out proper repairs at his Coney Beach amusement park at Porthcawl, Mid Glamorgan, before the incident during the 1994 Easter holidays.
Outside court, Mr Morgan, an insurance agent, of Cardiff, said: "I am extremely distressed and disappointed by this sentence. It was too low. We expected it to be substantial."
Mr Morgan is now to pursue civil damages in a bid for compensation.
Earlier, the judge, Mr Justice Curtis, explained that his powers under the Health and Safety at Work Act were limited to the imposition of a fine only.
He pointed out that a manslaughter charge had been considered but rejected by the Crown Prosecution Service.
"The fine cannot and does not bear any relation at all to the value of the life lost or injuries inflicted for the reasons I have explained," said the judge.
He said some might think that, as there had been a death, a more severe penalty should be imposed, but his powers were restricted by the Act.
The court had been told that Timothy died as a result of "an accident waiting to happen".
An unknown employee failed to secure the lighting archway over the track with bolts. A plastic cover carrying wires to the light was reattached and hid the fact that bolts were missing.
The error was not spotted before Timothy and his family went on the ride.
The judge said he took into account Evans's good safety record in 50 years in the business and the fact there had been no previous complaint.
He also ordered him to pay pounds 3,500 prosecution costs.
Later, Evans's solicitor, Nicholas Pounder, read a statement from the fairground owner, which said. "Words will never adequately convey my sorrow at what happened nearly two years ago, although I wish to express my heartfelt and genuine condolences to the family of the deceased child.
"I hope that the manner in which these proceedings were concluded today can at least in some small way enable the family of the deceased and injured persons to come to terms with what has happened."Reuse content