It was recommended as a place to visit from member of the local slots club, and Thursday is the only free day to do it.
And yeah, I understand. I had the same thing happen to me when I went to BC when I was 18. Only person on the trip to be left at the hotel while everyone else went out :/
The castle took about 45 minutes. I find the hardest part is trying to fit the correct parts together since a lot of them tend to not want to fit without having to file down the extra plastic on them.
I've only seen the movies but by far my favorite is the Sorcerer's stone, based on the fact they actually spent time with the school year / going over the magic. I dislike the deathly hallows the most as it just seems to go on forever with a lot of small talk / other stuff void of the main storyline (My opinion only).
As the houses go, I still think that Ravenclaw is the best house and should have gotten more recognition.