Sims will become the third member of his family to play in the annual pre-season feature match after brothers Ashton and Tariq but won't make his Dragons premiership debut until round three due to a suspension incurred last season with Brisbane.
He had initially feared also missing St George Illawarra's pre-season trials against Newcastle and Souths but received a clearance to play and intends to make the most of his limited opportunity to impress McGregor.
"I had my brother Ashton play here at the club and play in many Charity Shields and now Tariq is playing at the club and has played in a couple of Charity Shields so it is good to get the opportunity to do it myself," Sims said.
"Unfortunately we couldn't get the Charity Shield included as one of my suspended games but I get to play a game of football and it is just good not to be sat on the sideline for the whole pre-season.
"I think it is very important that I can get out there and I can actually run around with some of the lads and work with the different forwards we have at the club. They've got an immaculate forward pack here that I'm trying to break into."
After starting at lock in last weekend’s 18-10 defeat of Newcastle, Sims appears the most likely replacement for Jack de Belin if the NSW State of Origin forward is stood down while he defends aggravated sexual assault charges.
A decision on de Belin’s immediate playing future will be made after Thursday’s ARLC AGM but the 27-year-old has been ruled out of the Charity Shield due to concerns by the Dragons over his welfare.
Sims will line up alongside Test forwards Tyson Frizell and James Graham for the first time on Saturday night after they were rested for last weekend's trial against the Knights at WIN Stadium.
"Tyson is a class player who has obviously played a lot of representative football, and the same with James as well," he said. "They're key parts of the Dragons' forward pack and they're going to be raring to go.
"Depending on when Mary wants to put me back in the side after my suspension I am looking forward to working my back into the team."
Besides the opportunity to play in Mudgee, Sims is looking forward to catching up with Rabbitohs mentor Wayne Bennett, who lured him from Wollongong to Brisbane as a teenager.
Bennett was still in charge of the Broncos when Sims decided to return home late last season.
"I always thought he would finish at the Broncos but behind closed doors he obviously had some things that didn’t work out for him up there," Sims said.