I think I made the resi 4-5 weeks in advance, and they were extremely accommodating about everything. I don't recall having a problem, but I don't know how 'seasonal' it is (we went in October). I'm not sure if they book up way in advance?
The hotel people typically stay at (since the castle hotel is obscenely expensive) is Hotel Weiss Kreuz in Thusis, from which they picked up and dropped us off free of charge. The hotel is clean, well run, but no frills. I think we got it for $120? Again, may be seasonal pricing.
Their smoking room was simply phenomenal (cigar room). Again, it's more like an entire castle chamber, decorated ornately and painted in red, with lavish furnishings, and a crackling fire. And you pretty much have it all to yourself, perhaps for maybe a couple other people. My wife would have killed me had I smoked a cigar there, but I went in multiple times just to see it, because it was so beautifully done.
Unfortunately, there is absolutely nothing to do in the immediate area, as far as I can tell. What we did, was drive Furka/Grimsel/Susten earlier in the day. The actual way we did it was leave Thusis at 8/9 am, drive the passes (including Oberalpen) and then drive back for dinner. So in that sense, there
is stuff to do, but it's not in the immediate vicinity. Instead of arriving at noon, I would drive to one of the passes that isn't too far away, and do that until dinner.
edit- Thusis or Furnstenau to Andermatt via the Oberalpen pass is 2 hours one way on google maps, so if you arrive at noon, that is plenty of time to drive that pass and back. Andermatt is a pretty cute town that might be nice to grab lunch in anyway.
edit 2- I'm pretty sure they had free "all you can drink" house made brandy at the very end of the night with your little complimentary chocolates and pastries in the greeting/departure room (picture below), where you could hang out and get blasted if you hadn't had enough to drink by this stage ;P Of course, it's night time when you are there so the lighting is softer and warmer.
