The journey was once part of the vacation. Hell, the journey might have been the vacation.
There’s an arcade cabinet in the game room of the last postcard, but I can’t identify it. Paging Brad Conrad!
UPDATE (11/12/15) Tom at Garage Sale Finds nailed it. The game is Midway’s Stunt Pilot from 1971. The copyright date on the postcard is 1981, but clearly the photos are from the early ’70s.
2 Warps to Neptune 
I think that’s a Midway Stunt Pilot.
http://tinyurl.com/nzlalp3
Amazing. Damn fine work, Tom. Will update the post in a bit. The photo was clearly taken earlier than ’81.
Based on the fashion and hairstyle of the woman playing pool, I guessed 1971 which was the year Stunt Pilot was released.