For the wedding day recommend staying the Asian side of Istanbul. Travel will be more convenient. But if staying for a week or more can split the stay with Asian and European site. There is more touristy stuff to do on the European side. Below is a video going through different areas of Istanbul and where to stay: https://youtu.be/wzTVa4a6tvA
Turkish airlines has direct flight from most major cities in the USA. Once at Turkish International Airport can take a shuttle, bus,or taxi into the city. Taxi will be the most expensive option but most comfortable. It’s about a 30-45 min trip into the city.
The wedding venue provides a cocktail menu consisting of about 7ish appetizers.
There won’t be any alcoholic drinks at the wedding but feel free to pregame or go after.
Below is a link that divides it more into regions but I recommend going to Mediterranean coast especially since it’ll be perfect trip for summer. Most cities are a short flight away or car rentals are also an option. If time in Turkey is short can also fly to Europe to explore in couple hours for relatively cheap. Some cities to consider are Ephesus, Cappadocia, Fethiye, Antalya, Dead Sea Region(Oludeniz), Pamukkale https://www.lonelyplanet.com/articles/best-places-to-visit-in-turkey