Are there problems with handwaving attunement for timebounded adventures?

I will be running Strahd Must Die Tonight! for 5e and in previous games of it, due to the real and in-game time constraints and lack of short rests, I have handwaved attunement and allowed attunement to magic items just before the climax.

Are there any rules that speed up attunement that should be considered? Are there any mechanics of attunement to take into account for one-shots? Are there any compelling reasons not to allow players attune to items pivotal to the game?