I'm sorry that you had a disappointing visit w/ the Fila at the SPCA
but as they say everything happens for a reason and perhaps he wasn't meant to be with your family. Big time kudo's to you for doing your homework though! I would be hesitant to bring a Fila home with little ones only because you'll be having lots of strange little kids in and out of your house at some point.
I would second, third, forth?
LOL the suggestion about a Newf or Newf mix. We share our home and heart with Finnegan a 5 year old Newf and he is just AWESOME with kids. He actually cries and whines when he sees children because he wants to go and see them. Their size alone is a great deterrent for possible threatening people. Lots of people cross the street when I walking Finnegan because he is huge and black, even though he's the sweetest dog ever.
I also have a Dane that is great with kids, although much more boisterious that the Newf. She is VERY active although that is not "usually" a breed trait. It can vary depending on their lines.
I have met many OEM's that were wonderful family dogs although I know someone that just returned hers to her breeder because the dog was less trustworthy around strange children.
Good luck with your search!
Jen