Does anyone use a moveable pen in a small backyard?

[Brahmamama4]

I'm going to have 4-5 chickens and my backyard is not fenced. They have a 6x12 pen with their coop inside that is off the ground so they have more square footage, but I really want to give them some yard to play in the grass and dirt. I was thinking of making a little moveable pen to put them in for a few hours each day and move it around the backyard. Is this an ok idea if I have a pretty small backyard or will I just end up with dirt for a yard? Lol advice please!

 

[Imp]

If you move it around often enough, the grass should have a chance to recover.
How large is the backyard and how much is grass?

Imp- will probably take some trial & error.