I haven't looked at the book in awhile I just know they used Seaview at some point.
As for the movie being a sequel and because of that it can't be more stories about the same family in the family house, that's the unique thing about DS. Even on the TV show they retold stories and changed them in parallel time. This movie could be looked at as a sequel, it's just in a different time band.
I know, in a different time band they could live in a different house.
Lyndhurst is a cool looking house. I love it. It isn't Collinwood but it is beautiful. Graystone on the other hand, I really wasn't impressed with, not even when I went to see it. It isn't ugly but it would be better for a Dallas movie.
I hope this movie is good, I wish someone else was writing it and that's more important than what house they use, but if someone made a movie based on Dracula and put the Count in a ranch style house it just wouldn't fit, so yes, the location is very important to any story.