Mr Parsonage and his team from the Glasgow Humane Society will be part of the weekend celebrations on the River Thames, when they will row a 14ft 6in replica of the rescue boat George's father built in 1954.
Sunday afternoon's trip will take them along a 10-mile route from Putney to Tower Bridge.
The 68-year-old will be joined by colleagues Kenneth Bryce, Mark Craig, Antony Coia and Mark McKay for the once-in-a-lifetime experience.
Mr Parsonage said: "My father built a boat using his knowledge and the knowledge of others. It was the fastest boat you could row and still retrieve someone from the water without the boat tipping over.
"The original is now in the Riverside Museum, but I built a replica and that is what we will be rowing as part of the flotilla at the Jubilee. It is all beautifully decked out ready to go."
The friends set off from Glasgow on the 400-mile trip to London by road, with the boat on the back of a trailer.
Mr Parsonage saw an advert for the Jubilee flotilla in a boating magazine and decided to apply.
He said: "The security checks were extremely stringent, as you would imagine, but we got the clearance and are very much looking forward to the experience.
"It is going to be spectacular seeing all those boats on the Thames at the one time.
"There are so many boats I am looking forward to seeing and it is going to be fantastic."
The 10-mile route is enough of a challenge, but the team will have a total journey of around double that on the water.
Mr Parsonage said: "The camp is away so we will have to make that trip to get to the starting point.
"Then we have another trip of about five miles to get to Millwall docks, where we are due to get the boat out of the water.
"We will be at it from 8am to 8pm, so it will be a long day, but certainly a memorable one."
To find out more about the Humane Society's work, see the website: www.glasgow humnanesociety.com
l Don't miss Monday's four-page special on the Diamond Jubilee celebrations.