i know there is on which says " now i lay me down to sleep , i pray the lord my soul to keep , and if i shall die before i wake , i pray for you my soul to take"

I know exactly what you mean. There is another version - "now i lay me down to sleep, I pray the Lord my soul to keep, may Angels watch me through the night, until I wake in morning Light, Amen."

We say our prayer as a family at dinner. We thank God for the day and anything extra special that happened, we ask him to look after people that are unwell. We are teaching them Hail Mary at the moment as well, as it's one that they hadn't heard before.