I traveled to Paris many times as a tourist. First, you do not need a long telephoto. I took it once with me, but used it only for architectural details, and only because I had it in the bag. Since then I only take a medium zoom, a 30mm fast prime, and an UWA - 10-20mm. Paris streets are narrow, the buildings are big, an UWA is a must.
If you are a typical tourist like me, your 18-55 is good for daylight. No need to borrow another lens. Your 55-250 will be just a deadweight. The 50mm will be good in museums (I can confirm, D'Orsay does not allow photography). And get a used Sigma 10-20, it is relatively inexpensive.
Most important, enjoy your trip, Paris is one of the most fun cities in the world!
Thanks - sounds like I may just leave the 55-250 at home and bring the nifty fifty with me. Will look around here and FM for a used UWA as well.