If you're all about the culture and day trips, leave the rest of the booking to your holiday buddy. You'll have all of the quirky museums sorted, and they'll have the restaurant and hotel booked. You both get a bit of a surprise, but nothing gets forgotten.
Top tip: Only do this with someone you really, really trust who has the same budget as you. Otherwise, your getaway might be somewhere five-star when you were hoping for cheap and cheerful.