I don't see what's wrong with either the posting of this announcement or the event itself. There is nothing here whatsoever to suggest this is a 'bash Cedar Fair' party (whether such goings-on actually occur, which I guess will be inevitable in some quarters). There isn't even a mention of efforts to save Big Dipper.
I just don't see how being nostalgic for a vanished amusement park could be construed as a bad thing. I might even consider going myself, except I'm tired of being carried to tears thinking about it.
My author website: mgrantroberts.com
I'll tell you why I'm removing the post:
1) It has no attribution.
2) It promotes an event with no Web site to get its legitimacy.
3) It asks for money for the event.
If you want to promote something like this, submit it to news with full attribution, and if I think it's newsworthy, I'll post it.