
At around that age my bitches have always stood to feed the pups rather than lie down - they seem to wean themselves that way. Bitch has fulltime access to the pups (though she can get away when she wants by jumping the barriers!) at all times, and they're still allowed a quick 'comfort suck' even on the day they leave for their new homes. :)
Edited to add: If mum stops feeding them totally at about 5 or 6 weeks they'll need more meals and fluids from you ...