Mommy bunnies only visit the nestbox once or twice a day. Take the babies out and look at their stomachs. If they have fat little bellies, she is doing her job. We do a nestbox check once a day from the time they are born. Make sure your hands are clean and pat Mommy first (this gets her scent on you and keeps the babies calm). Enjoy!
She'll do it at night since their pretty nocturnal. I guess if they don't die she's taking care of them. I know thats not really helpful but rabbits do most of the work with their babies.
Babies that are getting enough to eat will be quiet and sleep a lot if they are really load and moving around a lot I would check their bellys. I have a doe that takes great care of her babies thank goodness. She is due in 21/2 weeks.