There's nothing wrong with approaching them and politely asking if they could try to be a little quieter for the sake of passengers in the front rows.

However, I never set foot on a redeye without the means to block out light and sound (a good eye mask and earplugs respectively). Yes, the crew should be considerate, but they won't always be -- and other passengers could just as easily keep you awake with their reading lights or conversations. I'd rather prepare for the worst and get good sleep than be kept awake on a red-eye (whether I'm in the "right" or not)