I'm not planning a TTD session, but I think doing it before guests arrive so you don't have to take time away from them is a good idea. Especially if you, like me, are using the week as an opportunity to hang out with all of your loved ones. As for your FI seeing you in your dress, I planned on doing our photos right before the wedding ceremony so that we can enjoy our cocktail hour and I'd worried about this too. I think that the first time he sees you in your dress will be special, no matter when that happens. And maybe you could do hair or makeup different than the actual wedding day so you can still have a surprise for him and "wow" him all over again. My only concern would be cleaning/pressing the dress in time for the actual wedding day. But if you're not going to totally trash it and you have 3 days, that should be OK! Or, even better, get a cheap knockoff or off the rack dress for TTD! Then FI doesn't see the dress and you can do your worst to the dress!