a small playground for young children ([MW])
Designates special play areas set aside for children, particularly pre-school age children. (gohistoric)
More usage examples, etc.
“Tot lot” is a Parks expression used to describe a space used for the recreational purposes of small children. (NYCity-Parks)
In Oklahoma City a number of tot-lots … are incorporated into the development of subdivisions and also you will find plenty of back yards with enough area and play equipment to qualify as a suitable tot-lot. (imaginativeAmerica)
A tot-lot in Pigtown, South Baltimore, MD.