That would not bother the time travellers from the past with their secret time machines hidden from the eyes of the public. They can still travel to the party in their future without running the risk of a paradox.
A future self of mine will come back and intercept Herr Adolf.
I hear Pompeii was very nice that year.
I’m trying to figure out what tense you guys are using. Is it the pluperfect subjunctive intransitive?
Hey, I will be was there!
It will be was a small little gig.
Mike Ween will be was there, too.
Plus Joanie Baxter and Bill Jones.
We will chatted a bit and go/went home.
Okay, so we’re not famous or anything, but we were there. See, the key is that famous people can’t time-travel because their presence will be noticed.
But Mike, Joanie, Bill, and I did fine.
OH! :smack:
I guess that means we’re nobodies. 
–G!
…this was perfectly natural and nothing to be ashamed of, because no one was really poor - at least no one worth speaking of.
…–Douglas Adams
…Hitchhikers’ Guide to the Galaxy
The first thing I am going to do when I make my time machine is go back to Hawking’s party, get everyone’s name, then go further back in time and kill them all. Or go less far back in time and kill them before they go further back in time to the party. Then just for yucks I will kill my own grandpa before he meets my grandma to hide the evidence that I was ever there.
I was going to suggest you already…have, but that last one stopped me.