Running with three wheels

I was originally going to run with my son in a babyjogger in a forthcoming race - unfortunately due to "rules" I would not be allowed to cross the finish line with him and technically I'm not allowed to run with him anyway because there is nothing in the "risk assesments" that were done.This is the first time I've experienced this beaurocracy having run in previous event such as Barns Green half marathon with no problems. The entry form didn't say anything about "no pushchairs" just "difficult for wheelchairs". Although they haven't said I can't run with him it's obvious that I would cause upset if I did.
This is the first time I've encountered this problem- what's the difference between a babyjogger and a wheelchair then? If it's a case of safety the jogger has brakes and a safety leash, tailor made wheelchairs go a lot faster and could cause more damage.
Rant over, still running in the race minus son and babyjogger. Ho hum.