Hi Hilary!
Bless you for adopting two of the most adorable dogs you'll ever meet in the world (ummm....I'm a bit biased).
I can share with you that my first Newf, Barkley, was adopted into our home apparently because he had "ran away" from his first home.
In the first week that he was with us, he got out of our yard and we didn't know. My neighbour came to the door to tell us that he had been standing out in the front yard, staring at the house for about an hour.
His loyalty and love for us was unwavering - and we were at least his third home.
I've also just adopted another newf, Anna. She came from a very loving home as well, and she seems to be settling in and being an equal opportunity loving dog just fine.
Good luck!!!