If you can raise the "house" part of the coop (the enclosed indoor portion) up so they can use the ground underneath it as part of their run, then you would have whatever's the square footage of the playhouse as your indoor portion (4x4?) and 32 sq ft of run. Which is not bad at all for 3 hens.
If you can't do that, and are stuck with only 32 sq ft total, you can try 3 hens if you want, there are a reasonable number of people who've kept chcikens at that stocking density without major problems, just recognize there is more chance of problems arising than if you had just 2. (OTOH with 2 chickens you're in the awkward position where if you lose one of them you really oughta get another hen to keep the survivor company and then you get into all those social-order working-out-the-food-chain kind of pecking issues, whereas if you start with 3 hens, you can lose 1 and still have "a flock" rather than a lone and lonely hen).
Good luck, have fun,
Pat