I'm not going to attend Friendsgiving this year.
Why are you going to flake on friendsgiving?
Thinking about it, nothing about it sounds fun.
If something doesn't sound like fun and you're not going to want to attend, then it is completely fair to let the people know right away so that they don't plan for you to come. At this point you should go, or else you'll be considered rude by your friends and they'll never invite you to anything.
I'am not going this year.
While it's fine to not accept the invitation to an event that doesn't sound fun, you should make good on your promises to show up. If you end up just flaking out it will most likely upset people in your friends circle.