That is probably a Studebaker goat cart. They were sort of promotional toys made to look like the full sized farm wagons the company made through 1920. In farm areas a boy might get one when dad bought a new Studebaker wagon. In a city like Chicago that wouldn't be very likely unless your dad lived in a very rural area and had pet goats.

Studebaker discontinued manufacturing horse drawn wagons after 1920, sticking only to the horseless ones that were becoming popular by those days. But the Studebaker-designed goat wagons continued to be manufactured by a toy company until World War 2.

Your father probably didn't get to really ride much in that wagon. They were often owned by photographers. Both goats pulling carts, and donkeys were popular photographic props that children were posed on.

The photographer came by. The animals attracted the kids, who flocked to the photographer. They posed for their pictures, to get to ride the wagon or donkey. Then the photographer hit up the children's parents to buy prints.

Apparently your grandparents did.