You'll likely get to hotel by 7 pm. If you choose S-met, there is a large open air restaurant/nargile lounge that has entertainment. Don't recommend eating there and they don't serve alcohol. We saw a dervish performer and the music is always good. Prob lots of smoking places when you wander around other areas. You should try raki sometime, too.
Many S-met sights can be done in half day, add walking to Grand Bazaar. Spice market is great and near ferry port to Asia. There is also a special mosque next to both that has beautiful tile work--quite impressive.
After a closer look at Buyukada, I see you, you romantic little devil!! Everything in IST has a certain romantic mystique. Learn about Roxelana and impress the little woman, too. Ignore those carpet guys, museum "guides" and restaurant hawkers. Have a wonderful time.