Other options for things to see
Blue Mosque
Might be worth checking if it’s still under renovations inside
Basilica Cistern
Surprisingly cool to see, doesn’t need to take too long
Grand Bazaar
Noteworthy, but a bit repetitive to spend a long time. Rick Steve’s has a walking tour for this in his book.
Topkapi Palace
The main Ottoman palace, would probably need some time for this
Spice Market
Included in Rick Steve’s Old Town Back Streets walking tour
If you have time, can take the Old Town Back Streets walking tour back to the Golden Horn