Looking for place in North End
I love Antico Forno. The food is terrific-service is excellent-reservations are a must because the dining room is small. The food is superior to many other larger North End Restaurants. It's been my best North End dining experience hands down. I think its the best way to spend your money in that area- The last time I ate at Saraceno's my salad was completely wilted!
I think L'Osteria is a good family-friendly place. Don't know if they have a kids menu per se, but I was there some years ago when the owner's young kids (about 12) were busing tables and it's still owned by the same family. I doubt pasta with butter would be a problem, but you could call and ask.
It's not gourmet, but a good solid consistent mid-priced family-style Italian place that's been in business since before the North End got yuppified. Locals eat there. I love their antipasto and the veal agrodolce.
Antico Forno is another place to consider if the kids will eat pizza and the adults want other options.
Avoid La Famiglia.
If you get there early enough, kids LOVE being allowed to pick out special chocolates and lollipops at Dairy Fresh Candies on Salem St. I think they usually close at 6.