My major concern is that the current plan comes across as:
"Hey, Shikamaru! You need to tell Ami about the wedding for your own safety, so we'll do that for you and even get her into the city in exchange for twelve days worth of effort from you. By the way, you're going to need to figure all that out because we've got nothing beyond 'write a letter and hope for the best'".
"Hey, Hazou, Ami has known that the wedding was going to be immediately after the exams since we had our... discussion, the Nara have channels of communication with the Mori you cannot imagine, and I am perfectly capable of writing my own damned letters thankyouverymuch."
Followed by:
Dearest Ami,
I write to inform you of your sister's imminent wedding. I offer to help you attend as long as you do all the hard work of figuring out how to smuggle a foreign jounin into a crowded clan event inside a fortress city without endangering my goals because my ideas have petered out at 'write you a letter'.
By the way, you hella owe me another favo-
"I've literally been standing right behind you for 36 hours."