I generally begin to ween around 6 weeks of age. Starting with a nice high quality wet (canned) food. I let the mom go on nursing for as long as it doesn't start to take a big effect on her, or until they are at LEAST 8 weeks. But normally by 8 weeks the kittens are nursing very little, if at all.
By 7 1/2 - 8 weeks, I start to mix in a little dry food with the wet food, as they get older I give them wet and dry seperatly, say if the kittens didn't get adopted until about 12 weeks old.
Even for kittens as old as 12 weeks it's good to give them LOTS of food, they grow so much and quick, that it's completely normal and healthy for them to have a little botta belly due to food intake.
You'll just have to be careful to feed them proper amounts as they get older so that they do not become obesse adults!
Hissy is right about the milk and creame, none for either.
The mother should still be eating about the same way as when she was pregnant, wet food and dry food offered serveral times through out the day.
Some people like to leave dry food out all the time, and offer just wet food periodically. Along with any healthy treats, or cooked meat.