You could try a time-out. They worked really well with my puppies. It has to be a reasonable time-out, though. For example, the puppy gets excited and starts mouthing and play-biting. Give one warning, "no biting," in a firm voice. The next time the puppy goes for the chomp, say, "right, time-out," and put the puppy in its bed (or somewhere safe) with a chew toy, for about 30 seconds. No more than a minute because the puppy will forget why it's there. Ignore whinging and screaming. Then, once the time-out is over, just bring the pup back to where it was before as if nothing has happened. Don't make abig deal out of it. The aim is to teach the pup that biting leads to an end of the fun. NOT that it will mean a scary punishment. An end to fun is a great deterrent to a puppy who is living to play! You sound like you have a lovely, happy, curious and very normal puppy!
ETA: An alternative is to simply walk away from the pup as soon as it starts mouthing - kind of a reverse time-out. Return a minute later and try again. Of course, this won't work outside...
