I'm not sure what you mean with the bday party example. But for the other one, the way I handle it is to consider things like this as reference material. Sometimes I'll read a mention of an attraction in a city that I have no immediate plans to visit, in fact may not ever visit. And yet should I go I would like to see the info again. So I collect it as reference material. The only gotcha is that I need to remember to check thru my reference material pertaining to that destination before I go, but that isn't too difficult a habit to form. "let see, I'm going to X, wonder if I saved any notes about that?" seems to cover it.