Lots of younger folks don't like mantel clocks...they are noisy, require winding every week and if it is an original (antique) then they look ugly to some. I have several antique clocks, but don't have them all running because it does get annoying, and one was so loud when it chimed it would wake up our guests upstairs.
I say respect your DILs wishes and let your son and her work that clock thing out on their own.