My ds is 5 1/2 yo and is too, very physically active! In the winter, I enroll him in swimming lessons, which he loves. And I am also looking into gymnastics classes for him.
One thing that we do together, that is physically, is make up a circus act. I balance him on my feet in the air (while I'm laying on my back) and we sing circus music and I bounce him up and down. AND its a GREAT leg workout!
He also loves to play and wrestle w/our golden retriever, Boomer.
Best of Luck~
Lisa, Todd, Dane and Amber: & :::