In my family it would have depended on the newborn, our first two would have done fine. Our youngest had colic so I would not have done it if Walt himself came back to life and offered me a grand tour.
I took our youngest who is now 2 yrs old when he was only 8 weeks old! Quite honestly I think they are easier to tour DL with than say a 12 month old who wants to get out and walk or crawl and gets antsy very easily!
However, he was a good baby. (My oldest DS had colic - NOT FUN!)
We didn't fly (live in Northern CA). I do think flying with a newborn can be a little crazy. They require so much stuff!!