The Basic Idea
Each child chooses a different number from the list on their clipboard and makes up a sum/number problem to solve which would give that number. They write the sum on their card shape and hang it somewhere outdoors. They then take their clipboard and number list to find the hanging sums which match the numbers, writing the sums next to the numbers as they find them.
How to take it even further or make it more challenging
Differentiate by the type of sum, digits, different operations etc. by putting them on different coloured card.