"My wife bought us a pair of mystery trips for my birthday. She went to Barry Island, but I was sent to Coventry"All sorts of things to consider and adapt on the system ...
I would see the tickets as being a separate pricing exercises - pay £35.00 for one, £60.00 for a groupsave (up to 3 adults or 2 adults and up to 2 children). Valid for an outward journey any time in a calendar month to a destination only revealed on completion of purchase - out by any train, return by any train to arrive at your starting station within 60 hours of leaving there.
Published lists of potential destinations and proportions of tickets allocated to each of them
Helpline available via somewhere (this forum
? ) to help people work out their travel plans. And a web site application that generates a .pdf including your timetables and things to see and do it Chichester or Teignmouth, Richmond or Lichfield, Marlow or Swansea, Bicester or Bournemouth.
Connections to and from local stations included ... so if you're on a mystery day out / weekend from Bristol, you can start from not only Temple Meads but also Keysham, Parson Street, Bedminster, and stations to Sea Mills.
I could see a rather encouraging leisure market niche for these tickets - "Silver Surfer" trips.