Content type with buttons such as "I'm going here" and "I have been here"
I would take a look at the Flag module for this.  We have used this module for similar purposes with good results.

You should be able to set up “I'm going here” and “I have been here” as different "flags", and then enable these flags on the content types you need.  This particular module integrates nicely with Views, Actions, and other Drupal mechanisms.