7crossing's is key to OP's note and Msmoto's rifled on that. A DX lens on an FX body is sort of a wrongly directed question.
I would also agree with Mirtos that thinking of a small light kit for a budding wedding photographer pay big dividends.
To some that think that a wedding can't be shot with primes, poppycock - a polite-r word for something else. Takes a little more effort, a little more creativity, and uses the photographer's noggin and legs and literal works the room or setting, but it used to be done all the time with no less results than today. The zoom is generally a convenience tool, albeit you don't have jump around tables, push people out of the way, or get in their way. I like zooms, but you can still work with primes.
As to sharpness of primes, and this is coming from someone who has two full lens bags nearly 50/50 of both, maybe more primes than zooms, both are very sharp. I really don't think there's are sharpness edge to primes at all. The real reasons I see to use a prime are brighter f1.8 is much brighter than f2.8 in a dim venue. You can see what you're getting much easier - that's saying a lot if you making images. Secondly, they focus faster for the same reason, (this is likely more my feeling from older technology from film days, but seeing my image focus snap sharply and quickly still seems faster than any of my zooms). And finally, two things that need to discussed as one, depth of field and bokeh - primes are better to my eye.
As always, my very best,