My daughter is in 1st grade and really enjoys playing blackjack with me(Dad). It's an amazing metaphor for addition and gives some good entrypoints for talking about probability and decision making.
We play for candy. Surprisingly she hasn't eaten any of it yet. She seems to be balancing her desire to beat dad by having more candy and her desire to eat candy. It's been great bonding time too.
Next up, a similar game with other operations.