Q. Can a dating couple wear Shabbos clothing when dating during the Nine Days?
A. Shebet Halevy (9: 131: 4) permits on the onset. However, Halichos Shlomo (14: D’var Halocho  15) maintains that if possible it should be avoided, but in need it is permitted.    
Horav Shlomo Miller’s Shlit’a opinion is that it is permitted.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a