It might be flat but it OS quite far for people who don't regularly ride. The surface is also not fast rolling in some places, so I suspect it wild tale me about 5-6 hrs, even that is a big ask for a couch potato. Now imagine doing it on an argos special offer bike without padded shorts and you will see that the least experienced will be at a disadvantage.it could certainly make or break a team, and if I was doing it with beginners then I'd want them all to know there were legitimate no shame bail out options at falling and limlithgow.
If you really want to do it or something similar, I would think cycling to somewhere for something (eg bbq) might be better.