On your marks
You’ll need a noughts and crosses grid, big enough for everyone to see and six cards with P on and six with T on. For younger children you could make the cards different colours so they can tell at a glance which is which.
Divide the group into two teams and play the game like a normal game of noughts and crosses, placing the cards on the grid in turn to try to make a line. But before you can put a card down, you say a Please prayer if you’re on the P team or a Thank you prayer if you’re on the T team.
Swap over at the end of a game to have a return match.
With older children you might focus the game more by providing a newspaper for each team and specifying that they should pray for and about items in the paper.
With younger children you could have symbols or pictures as stimulus for prayer on each side: pictures of sick people, the weather, animals, a cross, a candle, a dove, things of natural beauty, food, houses, someone crying, local schools etc
You could specify that all the prayers should be about something that’s happened in the past week (the Ts) or that will happen in the coming week (the Ps).