I supported a couple of guys who did the scottish C2C back in 2003. Started on Skye and straight across to wherever it was. I drove ahead to planned stops to give them food, do repairs, and all that jazz. 4 overnights if i remember rightly and we did it in the autumn before the weather was going to turn , but after midge season. These were two guys who were fit and mechanically minded.
From my experience it really is worth it if you can get a chase car/van especially if you are doing it with people who don't cycle much. They really will not appreciate it if you ask them to carry 20kgs of stuff on the bike and they can't be trusted to ration their food/drink properly. Even for medium effort you have got to keep everyone fed and watered, or things will go pear shaped. Hungry and tired people are no fun to be with and worse if you are also hungry and tired.
Regarding food you absolutely do not want everyone just jamming gels in as this can cause a lot of probs if they aren't burnt off as quickly as they go in and a body is not used to them. Stomach cramps, the sh!ts, and sleep problems are things you do not want in the group.
The planning that went into the trip was extensive and lots of plans for things not going to plan. Don't leave anything until the last minute like bookings, bike prep, bike fit, maps, etc and the two things really high on the list are weather and midges if it is the Scotland trip.
Don't skimp on anything and make sure you have battery chargers or battery packs and medical kit, spare clothes, and so on. Make sure everyone is NOT starting the trip with brand new and unworn clothing and footwear as it wont take long for blisters, chafing, saddle sores, niggly knees and backs to start delaying things.
It is all about preventing misery.
If someone does not want to play by these rules then you need to find a way of leaving them at home because they will become an anchor, or mess the trip up. If the route is all road, and not mostly offroad and remote like the Scottish C2C , or you are planning to take an age to do it, you can be a little more generous BUT a lot of the same rules apply.
That is all i can offer.
