Interestin Mav-- (your wife's research) years ago, i remember reading that play-- and playground games were vital to learning-- that children learn bigger or smaller-- and develop an understand of size by playing "Hide and Seek". the better a kids understanding of How much space he/she takes up, and how he/she can hide in a space is a Math skill-- Kids who excel in Hide and seek, are displaying a deep understanding of mass/size relationships.

Ball playing also teaches math-- and all interactive play hones logic and language skills-- explaining rules, understanding rules-- etc.

Jacks (a ball and toy game) and Hopscotch teach numbers, and sequences... lots of things to be learned in old fashioned childrens games...

Here in NYC so much of that has been lost-- and i think it worse in suburbs.. childrens lives are so structured now. they have very little time for free play.