We have an acre yard and we felt it was much too big for very young puppies. When we were outside with the pups, we opened the gate so they could explore the whole yard, but all other times the gate was closed. Make sure the increased area is always puppy-proofed. This is because the pup will now have room enough to pee in one spot, but still be able to play in another. If this happens, make the size of the area smaller again.
Some accidents are likely to occur.
Take this into consideration as you decide where and how to increase the blocked off area. Know that accidents will occur. Another reason puppies have accidents is because they don't have very good control of their bladder yet. Please be patient and remember that they are just puppies. Tsuwa was just a big baby puppy, and loved to play.