Golden rough housing too much

Question
I have a 8 mos old golden and she loves to rough house with my 3 yr old, how do I get her to stop biting with she is playing?  I know she is just playing but she seems to bite a little too hard and ends up huring my son.  What should I do?  

Answer
Young Labs, which I know best, and other puppies tend to very bad about
biting.  You see a litter of them, and all the ones that are awake are biting
another one or themselves.  I am not even sure they realize that when they are
alone, if they quit biting, they would quit being bitten.  At 3 to 4 months
they are getting their adult teeth, and it seems they spend every waking
moment biting or chewing.  One thing you can do at that stage is to knot and wet a piece of cloth.  Then freeze it.  The cooling will soothe the gums.  Only let the puppy have it when you are there to watch it.  I maintain a Lab's favorite chew toy is another Lab.  Otherwise they settle for any person they can.  They keep hoping to find one that won't yelp and jerk their hand away, or growl "Bad dog." and clamp
their mouth shut.  Then offer a chew toy.  They keep trying despite hundreds
of corrections.   Another good technique is to quit playing and go away.   Be
sure to praise them when they are playing nice and not biting.

You just have to keep on correcting them, hundreds of times, not dozens.
Provide sturdy, safe toys such as Kongs and Nylabones.  Avoid things they can
chew pieces off and choke on them.  Keep them away from electrical cords.
Crates are essential for most young Labs and other dogs.  

The pet stores are full of toys that many dogs will quickly chew up into
pieces they could choke on or cause intestinal blockages.  If you are not
there to watch, stick to sturdy stuff such as Nylabones and Kongs.  Keep a
close eye on chew toys and quickly discard anything that is coming apart in
pieces.  Rawhide is especially bad because it swells after being swallowed.
These problems are the worst with, but not limited to, large, aggressive
chewers such as Labs.

Ropes from the pets' store quickly turn to hazardous shreds.   Ones I made
lasted much better.   Go to a hardware or home center that sells rope by the
foot.  Buy 2' of 3/4" poly rope.   Melt the ends, and tie  knots in it.   Get
them as tight as possible, put it in a vise and pound it with a hammer.  Watch
carefully, and be ready to discard when it comes apart.

The 3 year old may be a good approximation of a litter mate.  About the same size and enjoying the biting, until it becomes too rough.  The usual answer is 0 tolerance of biting.   It could be hard to discipline the 3 year old to refuse to have the dog bite at all.  Yelp and leave could be a good technique for the 3 year old to use.  Breaking an established habit will be hard.  This is why I bring up the rope.  Tug of War may be enough fun for both to forgo the biting.  Perhaps a slightly longer rope would reduce the chances of the dog biting when it shifted its grip.