Between 2 1/2 weeks is when the eyes will try to start opening and weaning just depends on mom's tolerance for those sharp teeth on her boobies.

When we've had rescued litters we start introducing them to food at about 4 1/2-5 weeks depending on how fast they've developed by then (i.e. walking, teeth coming in) and how tired mom is getting of nursing them. We get puppy weaning formula and mix it with dry puppy kibble until it's nice and mushy and let the pups "play" in it. This has seemed to be an effective transition from mom's milk, kinda like switching a dog's food, it's best done gradually. They shouldn't go anywhere before 8 weeks old because 1) they need the social interaction from littermates to learn bite inhibitions and social skills and discipline that only mom can give 2) they need a set of puppy shots in them before going out into the world and being exposed to who knows what.