My second cousin danced an English Waltz on her wedding and my aunt who married a year later a Quickstep.
I don't think there is an *official* "openingsdance", but personally I think the English Waltz is wayyyyyy more romantic! I remember being it very hard to learn though, because you turn...and turn...and turn...and......you get the idea
While the Quickstep is basically stepping backwards and forwards!
However, (almost) every danceschool has special courses for soon-to-be-weds, which includes both dances I mentioned above. You may want to ask for further info there. But on a personal note: I vote for the waltz!
"Carpe diem, quam minimum credula postero." - Horace