Let nature take it's course. When they are ready to eat, they will. Make sure you leave dry food available for them at all times. What does mom eat? They will sometimes begin to eat what she eats when they are ready. Remember all cats have different tastes. I have a little one who weaned off of milk onto raw food and cooked people food. She will not touch any type of dry or canned food. Luckily she eats the "complete" raw food diet so she's getting adequate vitamins and minerals. I have another little one who weaned from milk to Babycat by Royal Canin and raw meat. Now at 11 months that's all he'll eat. He won't even try to eat anything else, no matter what I offer him. Then again, his brother will eat anything you give him.
Let the babies make their choices when they are ready. Mom will wean them when she's had enough. She begin staying out of reach to them for longer and longer periods of time and they'll get hungry and be forced to eat solid food.