Three high level itineraries
Sultanahmet + Beyoglu
Get lodging near Taksim Square in Beyoglu and drop off bags
Activities in Sultanahmet until ~6pm
Do dinner and nightlife in Beyoglu
Walk or taxi back to lodging
Sultanahmet + Kadikoy + Beyoglu
Go directly to Sultanahmet and do activities there until ~6pm
Take the ferry from Eminönü to Kadikoy
Do dinner in Kadikoy
Take the metro (Marmaray) to Beyoglu
Do nightlife in Beyoglu
Sultanahmet + boat tour + Beyoglu
Do a Bosphorus boat tour