Gumball

[divine]

If it were me organising it, i'd split it into 'stages' that are easily manageable and let everyone spend a day here or there to enjoy things, then tot up total times at the end if you really feel you need an overall time for it all.

As APoL has suggested above really, it's a big event and spending a week on the motorway might seem a bit of a let down when it's all said and done. If you do it in stages, you can even 'force' the routes onto some more interesting roads so that even the road trip aspect will involve more enjoyment and more scenery etc. than your typical autoroute will give you.

(Suggested route on google maps has you on one road for 455 miles at one point...)