Does it have to be a chain pub...? If so, there's a big Wetherspoons (biggest in the country I believe) in Exeter itself up near uni....
Why not head north out of Exeter, up the A377 past Crediton, up on towards Bideford way, then about turn and back down into Exeter to the 'Spoons? There's some nice circuits to be made up of the A and B roads to the north of Exeter...
That way we're all pretty much where we started, so no-one has any further than they came to drive home again... Those who don't fancy a hoon about can just nip across town from the services and sit in the pub till the others return.... And drinks/food is cheap as anything, due to it being a 'spoons.