Games are the name of the experiences.
The game of concentration is a classic. This is where you have a matrix of cards face down. You turn them face up two at a time and try to select pairs. Those that are not pairs are placed face down again.
I once met a four year old boy (a student's son) who was an aficionado of the game and could beat the pants off an adult (unfortunately me).
Of course, most children’s activities will provide some memory stimulation. Simon Says, for example, is a good drill for executive memory. The child has to hold the criteria for a response in working memory while he processes the commands in perceptual short-term memory.
To me the ultimate memory game, for older children over 4 years, is chess. Here is a classic memory game with retention and recall tasks abounding on many levels.