Just wanted to say thanks for all the advice. Here's where we stand now:
She's almost 13 weeks old. Has only peed in the house a couple of times, and only when she was excited about something. Only pooped in the house twice, and both, we suspect, on a spot on a rug where a (now dead) cat had peed.
She comes when called. Sits on command. Lays down. Fetches most of the time. Leash trained as much as puppies can be. Does not leave the yard or run in the street unless she's following me. Sits at every intersection before crossing the street, sometimes even without being told. She never gets crated more than about 3 hours, and only then on Tuesday nights when my wife and I both teach. Other than that, we're here with her almost all the time.
She gets a long walk at least twice a day, and most mornings she runs, off-leash, with a couple of young golden retrievers in the enormous park around the corner from us. How enormous? 5 soccer fields are contained in it, but do not take up all the space.
We set up lots of play dates, like this one, with a friend's boxer:
They clearly have problems getting along:
A good friend has a springer spaniel who has become Molly's bestest friend in the whole wide world. That same friend's mother has a 4 year-old border collie who is her second-bestest friend.
We've been working hard to socialize her with other dogs, and the only problem we've had is with an 80-pound lab who is overprotective of a friend's new baby, but we're continuing that integration process now that we know about his being overprotective.
I swear, I couldn't have asked for a better experience with a puppy.
And on the "task" front, I'm devising completely devious things for her to do, such as getting a pig's ear out of a tupperware container. MUWAHAHAHAHAHAHA.