My 7 year old does this! This is how Jake wakes up in the morning. He has his breakfast, goes outside to do his business and then speeds around the house growling and trying to get Shelby to play with him. She sits on the couch and ignores him I never scold him for his growls, even when we are playing. He likes to tug on a toy while I hold it and he growls. As soon as I bend down and kiss his nose, he stops growling, gives me a kiss and sits to wait for me to throw his toy. I can kiss him on the nose while he's growling because I know he isn't going to be snappy and I know what that particular type of growl is, it's all a part of our play. There are times he gets a little too wound up and we just ignore him and he stops.
On growling -- some puppies growl in play and when excited. Tow of my adults do -- Tansy runs around growling and going into play bows!
Loving mom to Jake, Shelby and Micah