You could always cancel the reservation and make a new one with a romance package.
Or just call MR reservation line and make changes to your existing reservation. If you do get an email from Virtual concierge or someone at the property, make sure you let them know it's for a special occasion, and often they will make sure to get you an upgrade and maybe a little extra gift/service.

I was staying at Renaissance in Paris for a special occasion and got a full bottle of champagne and box of chocolate in addition to the regular amenity gift. Same thing happened when staying at the JW in Miami...