The Trump team will likely set up a large screen TV array or two outside to handle the overflow. The picture of the crowd outside will tell the story.
Be sure to print out a map with all nearby parking lots. There is a parking lot attached to the hotel on Granite Street but it will fill fast.
I attended the NH GOP convention in January and Trump spoke there. I had a FRONT ROW seat - just 40 feet from real POTUS - it was fantastic! So I will let others "have seats" next Thursday, LOL.