The 300 mile distance will be an issue with whatever choice you make but I think most true wedding reception venues will be able to handle this well.
We had our reception at Castle in the Clouds either the first or second year they started doing them. It's a beautiful location with the best lake view you could ask for. Back then we were allowed to choose whatever catering company we wanted but now it appears that they give you a choice of two - Harts and The Red Blazer.
The only issue with the Castle that I can see for you is lodging since I assume many of the guests would be out of towners. That means guests would be doing a bit of a drive to either Meredith or Wolfeboro. If it's a Saturday in the Summer, you can add traffic into the mix getting there from Meredith. (Fake edit - I forgot about the newly revamped Center Harbor location).
Church Landing from a logistics perspective makes a lot of sense - lots of rooms within walking distance. I can't speak for anything about their weddings though other than when I was a young lad I attended a portion of a reception there as an uninvited guest and it was a good time
