Writing Prompt: Write a letter or make a card for someone and send it to them in the mail. Grandparents LOVE to get things in the mail.
Math: Do a page of math problems, 15 minutes on Khan Academy, or problems in a packet/workbook you have a home.
Building/creating: Make a lego structure, a block tower, or some other creation with building blocks.
Exercise: Run a race. Run to the end of your driveway, to your outdoor play structure, or to the mailbox. Time yourself and see if you can improve your time.
Cooking class: We have been watching this kid cooking class at our house. Make lunch (or dinner) after watching it!