Well, as I mentioned above, I didn't see those two choices as particularly connected on my playthrough, except in so far as all choices in the game are connected. But it's your game, so if you say they should be, that's final. Code-wise, the structure you suggest seems unproblematic.
Shifting topic completely (well, sort of), I only just noticed that organizing the welcome party for the sister also gives a -1 (effectively -2 as you miss out on a +1) to the team score; I'd missed that earlier. Presumably if the party had made it into this update, there would have been an opportunity to recoup that point if the party was to her liking. Else I might have to replay that section at some point and doing the fashion show instead.