I'll just add my 2 cents, (again) as an experienced dog owner and RVer. I have camped with very large dogs, many of them on the common restricted lists, (pit bulls, mastiffs, GSDs). I have also volunteered at animal shelters.
You are venturing into an area with 2 big possible problems.
First of all: adopting a dog with an abusive past, a pit-type with an abusive past.
Second of all: You are planning on taking a pit-type dog, (with an abusive past) to public places with children/other dogs.
Many shelters/rescues will call pit mixes ANYTHING other that pit bulls. Petfinders is not necessarily a reputable place to find a pet. Just about anyone can post there.
If you are not familiar with large, powerful dogs with abusive histories-you should leave them for the experts, or plan on spending a lot of time with a specialist.
IMO: you should slow down and reconsider your options. Many dogs will appear great in a controlled environment, with familiar people-but you cannot predict their behavior in new situations.
I hate to sound so negative but I see people making this mistake all the time. The media/animal groups really put pressure on people to adopt, but it's an area that requires a lot of dedication and expertise. I'm specifically referring to powerful dogs with abusive pasts. Potentially dangerous area for the novice.