Personally I don't see the harm in mom going along -- it's not like they're going to get to be "intimate" or anything. Mom would LOVE to see her son!! I don't blame her! She's been worried sick since he's been gone, and she's dying to see him! No one has the love for anyone like a mother for her son! It wouldn't kill DIL to let Mom ride along. She and husband can still talk alone it they want, but at least let Mom SEE him.
Those are just the thoughts of another mother.