Brian probably hasn't met River, has he? You know...his other grandchild. That could be a fun little side story -- the adventures of River Song and Anthony Pond.
Very different family. River's older than her parents and Anthony is older than his grandfather.
As for the scene itself, I'm of two minds on it. It is a nice scene, but then TATM is already derivative of Blink, this would only have made it moreso.