I know it is best to get into town and use a bank but we just need a little to tip the taxi etc. is there an ok place?
Have you considered just using a credit card?
There are ATMs in the Istanbul airport after you go through security which will get you a better rate than using a money exchange. Though a little dated this thread has some info https://community.ricksteves.com/travel-forum/turkey/money-exchange-or-atm-in-turkey-euro-or-tl
FWIW I ordered some lira in smaller bills before my trip. Did I get the best rate? No, but I got one thing off my mind and worry for arriving in a place I hadn't visited before.
Are you flying into Istanbul? Here is what you need to know about Turkish lira-the largest denomination you can get is 200 lira. That is worth about $5. Crazy. Many Turks carry Euros, US dollars. Feel free to tip in dollars, use your tap and pay whenever you can.