Before I started flying the boxes, I always wanted to know who else was a qualified airman in case of an emergency. Knowing you have another useful crewmember in the back can be a real help for whatever the situation, so yes I think if you are in uniform you should stop in and say hi, paying passenger or not.
This is something else you might want to consider. Even if you are a paying passenger if something happens all the other cattle will be looking at you, probably even more than the flight attendant to do something just because you are in a pilot uniform......
P.S. why is it in your company manula to wear the uniform while traveling, is it a customer relations (P.R.) thing?