The 29 year old will join stars like Edward Norton, Anthony Edwards and The Strokes rocker Nikolai Fraiture on 1 November (09) when the big race takes place.
And Matthew Reeves is sure his dead mum and dad will be very proud of his efforts.
He tells In Touch magazine, "My father would probably wonder what happened to his son, who’s this imposter? Hopefully, he’d be impressed."
Documentary filmmaker Matthew and his sister Alexandra were elected to the board of the Christopher & Dana Reeve Foundation the day after their stepmother Dana died, and the marathon man admits he has felt compelled to do all he can for the charity ever since.
He says, "The injury happened to my dad, but all our lives were affected. We just do what we can to help."
The late actor was left paralysed after falling from a horse in 1995. He died in 2004. Dana Reeve lost her battle with cancer two years later (06).