This idea could be used for lots of things (memory verse words, for example, would work really well) but I'm using it for prayers to begin with.
There are lots of things that we could say thank you to God for, but we often forget to do so, a bit like having treasure that we bury and forget about! This activity helps us to remember to say thank you to God and also emphasizes the idea that the things and the people we have around us are precious like treasure.
Get the children to draw on little stickers things they could say thanks to God for: people, animals, food, nature etc. Stick the stickers onto plastic coins (you might need a bit of glue too, to make sure the stickers stay on!) and then hide them in a bucket of sand.
Take it in turns to dig into the sand with your hand and pull out a coin. Thank God for what is on the coin or ask God to bless them if the picture shows a person or place.