There's a lot you can do with coloured cards! Children really understand symbolism and even our 5 year olds had no problem with this prayer activity...
You will need a gold card and some double sided cards (green on one side and red on the other).
We discussed traffic lights and the fact that red means stop and green means go. We talked about how sometimes we do wrong things we wish we hadn't and that can make us feel bad and stop us going forward with God as we could do (symbolised by a red 'stop' card). God (represented by a gold card) will forgive us if we come to him and say sorry.
Each child thought of something they'd done during the week that they were sorry for and then symbolically brought it to God by putting their red card next to the gold card and saying sorry. Then, as a symbol that God forgave them, they turned the red card over to the green 'go' side.