When my son was small I was kind of "away from God", but with my daughter who is nearly 20 months, I usually say a little prayer when I'm cuddling her in the rocking chair before she goes into her cot. I talk about our day and thank God for the good things that have happened and ask his help if things have been difficult, etc - just simple stuff. I hope that as I continue to do this, when she is old enough, she will join in.
With my son, who's now 5, it would be very strange for him to pray himself. He's not been exposed to praying enough, if you know what I mean. I try and pray with him sometimes, but don't push it as that can have the opposite effect than the one I want! I'm trying to make him see how praying is normal at any time (not just bed time) and if something happens when we're out in the car, like when we saw a nasty accident, I said - I think I need to have a word with God, and said a quick prayer asking God to look after the people who had the accident.
Hope this is making sense - to summarise, I feel that it is important to show our children how normal and helpful prayer is to us, and pray with them, but I wouldn't expect them to pray on their own, unless I had prayed with them for years and they felt ready.
Clairy