*troublesome* can borrow a D50 instead of D60?
RGB Metering & Focusing.
And D60 cannot AF with 50/1.8. Have you seriously shot MF in a fast paced environment??
Plus, D90 better high ISO performance will be perfect for shooting ambient light shots with the 50/1.8 while giving you AF with the AFD lens.
From your questions, I really wish you good luck with the shoot. You will need lots of it. Enjoy and have fun.
Here is my take.
Just use the d90 wit 18-105mm and flash for most shots.
U will need to take some still details like flowers, shoes, decos thus u use the 50mm
I think this thread is not to debate how valuable are the photos to the couples. To each his own.
Remember that the photographer is also at times a impromptu coordinator, art director, MUA.
Have loads of fun and share ur pics.