The ex-Manchester United boss took a break from watching his former team's struggles at Old Trafford with a trip to Wembley.
And he got the chance to see a team lift some silverware this season after son Darren's Posh beat Chesterfield 3-1.
Ferguson junior, who once told his father to stay away from Peterborough matches as they always seemed to lose when he watched them, said: "My mum is a lucky omen for me!
"He's not see us win for a while, but then a few people who could say that this season.
"It's important that all my family are here, my wife and children are here. It's a good day for the family."
First-half strikes from Josh McQuoid and Shaun Brisley - both players' first goals for the club - put Posh in the driving seat.
Yet plucky Chesterfield hit back after half-time through Eoin Doyle and must have fancied their chances when Joe Newell was needlessly sent off for kicking out at Sam Morsy.
But Posh clinched victory in the 76th minute when Liam Cooper tripped Mark Little in the area and Britt Assombalonga tucked in the penalty.
Ferguson, who also won the JPT as a player, now has his sights set on a return to Wembley for the play-off final in May as Posh bid to bounce back into the Championship.
"The motivation now is to get back here, there's no doubt about that," he added. "We have to take this into our final games. It won't be easy but we have enough in that squad to do it.
"I said to the players that you only enjoy Wembley if you win. We have a good record at Wembley and hopefully we can come back."
Chesterfield, by contrast, have no intention of returning any time soon as they are challenging for automatic promotion to League One.
"I'm desperate not to come back," said manager Paul Cook. "We are in a strong position in the league with a five-point gap, so if we were in the play-offs that would be a disappointment.
"We're disappointed now. But we always take part in good games, we are a passing team who want to play the right way.
"Against a strong Peterborough side we matched them for long periods and looked equally as good as them."