As I use a wireless Xbox controller and my ipad is stationary (ie I don't tilt it for flying control) I use a near empty spray can, by putting it behind the ipad, wedged between the ipad and the cover. Spray cans are aluminium and they conduct heat very well. A thin and tall can works well for me. The hotter the spray can gets, the cooler your ipad will be - though it still gets warm. I use a starchlike chemical spray for ironing clothes - something not too toxic!
Don't recommend a full spray can or putting it in the fridge or an icepack - might be too cold for an ipad (I personally would not put anything too cold against an electronic device - any trapped air inside could cause condensation which could short circuit your device internals and kill it - I would not take the risk - room temperature is recommended). Room temperature works well for me. Don't use a full spray can as the pressure will build up and its best to be on the safe side when it comes to confined gases - always!. Use an empty or near empty one, or an empty drink can.
Just an idea.