Donna - what has worked us is: everyone wakes up VERY early day of the flight and has a normal day. On board we often don't eat the dinner meal, or just eat a little bit if it comes pretty quickly. We then take drugs - each one of us, including my children as young as 9. Son takes Benadryl, daughter takes Dramamine (regular, not non-drowsy), I take Xanax (I am afraid to fly but have no trouble sleeping anywhere if I am relaxed), and my husband takes Ambien.
My husband has trouble sleeping anyway. He has tried everything over the years-doing nothing, a glass of wine, TylenolPM, Xanax - without any relief. If he gets little or no sleep on the plane it really hurts him for the next 2 days. After being prescribed the Ambien, he tested it at home to see what it was like. First time he tried it on a flight it made all the difference in the world. We all have an active first day and wake up normally and feel great on day 2. Be sure to test drugs out first at home but we swear by them!