I'd recommend keeping the original canti brakes and getting canti-compatible levers:

1) It's cheaper- you just need the levers.
2) It looks more classic (IMO)
3) Might be hard to find V-brakes that are compatible with the narrow spacing (55 front and 65 mm rear) of the existing canti studs. V-brakes are made for MTB's (and modern touring bikes) with wider stud spacing.