Gifts and gestures
Barcelona experiences make straightforward gifts and honeymoon add-ons, and most operators will happily handle a surprise if you ask in advance.
A rooftop dinner
The default, and it works: book a specific table, mention the occasion, and tell the kitchen if you want something held back for the end of the meal.
A cava tasting
A half-day trip to the Penedès with a cellar tour and a tasting, usually bookable as a voucher with an open date.
A sailing or spa voucher
Both work as open-dated vouchers, which gives the recipients the timing and gives you something presentable to hand over.