My FI wants to wear a tux at our wedding.  We're having a 2pm ceremony, indoors in a "castle"/mansion.  I have heard that it's inappropriate for tuxes to be worn for events that begin prior to 6pm.  Is this still relevant etiquette?  On a scale from "I don't care at all" to "mortally offended", how much would you care about this rule being broken??  I want FI to have what he wants for his attire but I also don't want us to look ridiculous or invoke any eye-rolling...
Uggggghhhhh.  Unfortunately I know nothing about formal menswear.
*edited for a missing word*