June 9th!
You can arrive by 2:30pm at the earliest (obviously if you're in the wedding party, you are expected to arrive much sooner than this).
Plus ones will be approved on a case-by-case basis, as there is limited space at both venues. Email Caitlin at caihar128@yahoo.com or Allister at allisterhampton@gmail.com if you would like to bring a plus one. About a month before the wedding, Caitlin or Allister will reach out to you to confirm or deny.
Absolutely!
Formal attire is strongly preferred.