I also did not mind mouthing on my hands. I used Jean Donaldson's technique to use this time to teach bite inhibition; along with teaching commands for gentle/easy, drop it/out and leave it.
My pup did grow out of the mouthing and she has an extremely soft mouth. (Actually she has too soft of a mouth, which is annoying but that's another story. lol)
If you want to read about the method I referenced for teaching bite inhibition; click on the link below, and start at the bottom of page 63.
And yes, the running and jumping is playing.