I like to get a pile of organic matter, like old straw, going in the runners' day pen. After a while it holds worms that they can dig for. Planting oat and wheat seeds here and there in the pen is fun, after a few days they begin to sprout and provide greens.
A kiddie pool is a big entertainment center, and tossing lettuce leaves into the water livens things up.
I have made the day pen as large as I could fit in my yard, so it is 10'x16', with an attached 4'x8' house and same sized porch. There is a fenced garden area adjacent to that, and then there is the backyard tea garden. There is also a forest garden of 1800 square feet where we go once a day or as often as my schedule allows.