And I will split the difference.
Yes, update your information. All of it including if possible your new name and gender status. Do not make it easy to find you if there are possible weirdos.
No do not go to the reunion. It does not appear that you have had much contact with them in 50 years. No suggestions of having contact with old HS friends. Honestly to me they have forgotten you, as you probably have forgotten most of them. I graduated (1973) in a class of 500. I left town promptly (US Navy), left them behind. I ,for family reasons, came back and have some contact with my class on FB, but daily I go "Waa, who is that?", or Damn they are old" due to their postings or pics. Few I consider friends and I have been around to bond but have not. So my perception that your going to the reunion, Michelle, while it may be entertaining, I think you will walk away saying wont do that again.
Update for your own satisfaction and let the rest go. You are the new you with a new growing, enjoyable life to live. They are their same ole, same ole.