Agree - this doesn't sound like aggression.
My pups will do this with the adults to initiate play. If puppy is too rough, gently correct by redirecting the pup or allow the pup out separately until it is more mature. Just because your older dog is the same size as the mother does not mean the pup will automatically defer to the older dog.
Watch that the older dog does not correct the pup and do not assume dogs will work it out amongst each other. One rough swipe from the older dog can result in a broken shoulder or arm - be careful when letting pups and adults out at the same time.