As with just about any restaurant in town, a lot depends on your child. If you're child is well-behaved and the slightest bit adventurous, then it will be fine. Oh how I wish some adults fit that description.
We took our almost-six-year-old son there a few months ago for dinner (a Friday night, I believe) and it was fine. He shared some salami with his grandfather, ate far too much bread and loved the pasta with short ribs and chanterelles (well, I ate the chanterelles). He had the gelato tri-fecta for dessert, although I can't recall if he substituted a second cup of ciocolatta for one of the others.
He was well-behaved, and the staff reciprocated by treating him respectfully. Honestly, I've yet to run into a restaurant of Perbacco's caliber in this town to which I would not take my son. If you teach your children well, they'll do fine and the staff will love them. (And, as for finding something to eat, you can almost always find something for even the most picky eater. And I've never had a restaurant turn down a request for something basic. Italian restaurants, of course, tend to be well-suited to this.)
On a recent visit to SF we had lunch at Perbacco with our 6 year old and it was fine. There was no unwelcoming vibe from the waitstaff, at all. I don't remember seeing any other families with kids there, though.
Of course, this was lunch, not dinner. And our son is good about being in restaurants (we bring paper and he draws quietly until the food comes). What age is your child? (Or children? I think going to nice places with one child is not as challenging as taking multiple children...)
Our son loved the food, by the way: he and I split the tajarin and he had the gelati for dessert.