Charlie and I have a simple bedtime prayer routine. It used to be that I'd give the topic and he'd fill in the details. But these days (it's a 3 1/2 yo thing), he wants me to do the whole thing. It's a simple Thanks, Confession, Supplication, Adoration formula:
We thank you for all the blessings of this life (fun things today, list of friends, list of family).
We are sorry for everything we've done wrong. We know you forgive us and will help us do better when we ask (sometimes mention something specific here--usually MY confession)
Please be with everyone who is sick or sad or lonely, especially _____. For the people who are sick, make them well. For the people who are sad or lonely, make sure they know you are with them, and give them a friend. Help us to be friends too.
Give us a good night's sleep (any special intentions for ourselves).
We love you God, and we know you love us.
More recently, I've tacked the Lord's Prayer onto the end of it because I realized he needed to learn it at home and this seemed like the most logical way to do it.
The other night we were praying for a friend of mine who is an amazing teacher and doesn't know where she'll be working next year. So I said, "Be with __ who wants to teach, but doesn't have a place yet." Charlie stopped me and said, "She could teach kids to ride bikes!!!!" I told him she really likes math and would like to help kids learn to work with numbers. Then Charlie began counting to the tune of the ABCs and it was clear he somehow felt he was helping her by doing this.
Praying with your child is an amazing thing!