If you are uncomfortable with the heavy play, than tell them to knock it off.
But, they do play rough. Play is very different than fighting. Fighting will entail biting, blood, growling, shaking while holding, and possibly one dog screaming and trying to quit. You don't want to be anywhere near this level. Play often has some verbal aspect to it. The thing is, once you experience fighting, you probably will not want to allow any physical playing between two dogs.
Do you want to prevent them from getting good play and exercise because you are afraid that it will turn into fighting?
They are both large rough and tumble dogs. Roughhousing in the house is probably not a good idea anyway. I would train them that doing that in the house is not acceptable, and then I would limit the amount of time I let them run and roughhouse outside, quitting when you feel uncomfortable with it.
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