Leonard, the world's leading cap holder with 114 appearances for England, has offered to play at No. 10 while Jenkins experiences the dark side of rugby life in the scrum, but the Welshman is all set to decline the challenge.
"I've spent most of my rugby life trying to get out of the way of forwards so I don't think I'll be spending time in my last game in the front row. It's a nice try by Jason, but I'm going to stay with the backs," said Jenkins. "It promises to be a fantastic day out for everyone - the players, their families and the fans - and both Jason and I are delighted that we'll be bowing out in front of such a good sized crowd. The last figure I heard was that they had sold 18,000 tickets and hopefully a few more will turn up on the day.
"It'll be great to have Scott Gibbs alongside me one final time and I can't wait to have one last outing with Rob Howley. He's had a fantastic season with London Wasps and will be bringing the Heineken Cup with him to show off to everyone.
"At the last count there were more than 600 caps on my team and almost 400 in Jason's side, including three English World Cup winners. We've got two fantastic line-ups and there should be plenty of tries for everyone to savour.
"I noticed that Jason got in the mood last weekend at Twickenham when he scored one of the tries in the Barbarians' victory over an England XV and I'm sure he will want to grab a few more on Sunday. After all, props don't get many in their career."
There will be plenty of activity at the Millennium Stadium before the main event kicks-off at 3.00pm with three matches taking place between Llantwit Fardre and Barking, the two clubs at which Jenkins and Leonard started their careers.
There will be games at Under 8 and Under 9 age levels and then a 30 minutes each way match between the two senior sides. At half-time there will be a charity kicking competition featuring Newcastle and Wales soccer star Craig Bellamy, ex-Stereophonics drummer Stuart Cable, Wales U21 outside half Matthew Jones and Jenkins. Stuart Cable will also be performing a drum solo during the break.
Singing star Peter Karrie will warm the crowd up before the kick-off and the Royal Regiment of Wales Band will also be on hand. They will also play a part in the dedication of the commemorative stone that is to be laid at the Millennium Stadium to remember the 16 Welsh rugby internationals who fell in the two Great Wars.
NEIL JENKINS XV:
Kenny Logan; Justin Thomas, Allan Bateman, Scott Gibbs, Richard Mustoe; Neil Jenkins, Rob Howley; John Davies, Garin Jenkins, Ben Evans, Steve Williams, Chris Wyatt, Emyr Lewis, Brett Sinkinson, Scott Quinnell
JASON LEONARD XV:
Matt Perry; Nick Beal, Nick Greenstock, John Leslie, Jon Sleightholme; Paul Burke, James Grindall; Jason Leonard, Dorian West, Darren Garforth, Alex Codling, Billy Davison, Kingsley Jones, Neil Back, Andre Vos