Tunnels and tents! Our tunnel is one of my kiddos favorite things to play with. Tunnels and pop up tents are great for burning off enegry but they can also be good for quite time too. How you ask?
Throw in some pillows with a flashlight to read books. Make a fort and build a hide out.
Don't have a tunnel?
Cardboard Boxes are great for doing the same thing. Plus when you are done you don't have to store them.