I'm curious about why your 100 lb dog is okay but the Rottwieler is not? Their big and look scary, but so does your 100 lb dog. You're comfortable with it, presumably, because you trained it and trust it. But it snapping would have the same high consequences as the Rotty.
I guess it comes down to whether you trust the people to train the dog properly. If not, any dog of significant size would be a problem.
As noted, no one can tell you what you should be comfortable with, especially involving your own kids. I just found it a little odd.
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