But Regan said: "I was asked to captain the Barbarians and I consider it a massive honour to do that.
"I'll be leading out the side at Twickenham alongside my children Daniela, nine next Monday, and Alexandra, six, and it'll be a very nice enjoyable family day."
Jason Robinson is named at full-back but his fitness is being monitored closely.
The cross-code star was substituted in the second half of England's 15-6 World Cup final defeat by South Africa last month because of a shoulder injury.
Barbarians coach Eddie O'Sullivan is confident Robinson will be ready for his last competitive match before retiring from the sport.
O'Sullivan said: "Jason has made a miraculous recovery after working incredibly hard to be fit for the game.
"He has been speaking to the Barbarians about playing in this match for a long time.
"He had a run out yesterday and was fine, but we are assessing him closely."
The Barbarians confirmed that Andrew Sheridan had been withdrawn from the squad due to club commitments, so Stormers prop JD Moller is drafted into the squad as his replacement.
The hugely impressive starting line-up features five All Blacks, including prolific winger Joe Rokocoko, and Wallaby star Matt Giteau at fly-half.