Sometimes our kids would have trouble sleeping or would show signs of "nerves"--little donkies on the edge, if you will.
With Aidan, our youngest, this would show up as restlessness. He'd be very obviously tired (rubbing his eyes) but when put down for a nap would refuse to shutdown and rest.
With the girls, this would present more as bad dreams or crankiness, whining over the slightest thing. Ruling out recent sugar intake, our next step would be to give the kids some children's b-complex.
Nerves are a funny thing. In the absence of B vitamins (B-6, B-1 in partcular) they start acting up. In fact, prolonged use of alcohol will deplete one's B-1 so greatly as to cause delerium tremens.
While our kids certainly aren't imbibing any alchohol, other things can deplete B vitamins, such as 'stress'. What I would call stress for kids would be things that are extra exhausting to the body, such as traveling, lack of sleep from a day of back-to-back birthday parties, etc. We just came back from a six day trip to CA and back to visit family. By the time we returned home, we were all physically drained. The kids were off their sleep schedules and were crankier than usual. Stress.
So it's times like these when we make sure we're getting at least a teaspoon of our favorite kid's b-complex into each child as soon as possible. For our baby, it goes into his milk. For the girls we have marketed this product as "no dream juice". (One night they were voicing their concerns to me about having bad dreams, so I seized the moment and offered "no dream juice" as the solution. That was months ago. They ask for it by this name every night before going to bed now.)
I suspect that the B-6 in this is particularly helpful since I have long used that vitamin to help me get a restful night's sleep. But I would never recommend giving a child anything other than a complete, balanced source of b-complex as giving only one vitamin at a time can cause deficiencies in other vitamins.
In any case, in times of "stress" or where sleep is becoming troublesome, we check to make sure the kids have been getting their b vitamins. World Organics's Baby Vite is a great source for that and a staple in our little donkies' medicine chest.
Small Print: I'm not a doctor, nor a nutritionist. Just a guy who has experienced a lot of trial and error and has read a lot about nutrition for my own use and to help my family. You should consult a nutritionist or a someone trained in nutrition if you have any questions or doubts about what to do. Meanwhile, if you don't like what I'm writing or disagree that's just fine with me. Stop reading. But don't try and pin all your troubles on me. Do your own research and make your own decisions based on your personal evaluation of the information.