is it tacky? (invitation question)

I was reading on the knot -that you are only supposed to wear long dresses to weddings that say formal reception - but NY weddings almost everyone wears long dresses to an evening wedding

I have a lot of guest coming fromthe sticks of western Pennslavania should i write
Formal Reception to follow

Is that tacky?

I don't want other people to wear tuxs - so i do not want black tie optional

thanks