Have set up befor going on a nature walk! - I love math that is so visual. This link will open to an article on Kindergarten Math but so many of the activities can be adapted to younger students, like the leaf activity pictured here.
Hide numbers throughout house or yard. Children hunt, find and arrange in order before timer rings. You could use this so many ways - larger numbers, equivalent fractions, rounding.Learn Through Movement - Number Hunt Math Game.