There are three seats in the back of the C-Class but, in truth, three adults sitting there won’t thank you on a long journey; the interior is narrow and the large central floor tunnel pinches foot space for the middle passenger.
Two six-footers should be reasonably comfortable, though, thanks in part to the decent leg room. While head room is okay, as a rule the optional panoramic glass roof zaps height; think carefully before ticking that box on the options list. Bigger cars, such as the Superb or Passat, are much better prospects for anyone who regularly carries adults in the back.
At least storage space is decent enough, with a relatively generous pocket in either door and map pockets on the back of the front seats.