Are puppies in harm because of flea 2 weeks old?

Fleas on puppies can be fatal. Treating the fleas is you don't know what you are doing can also be fatal.

Ask your Vet. I assume if you are breeding your dog that you have a Vet.

Here is a site written by experts: Safe Ways to Get Rid of Fleas on Puppies | The Daily Puppy (http://www.dailypuppy.com/articles/safe-ways-to-get-rid-of-fleas-on-puppies_774.html)

Fleas on young pups can cause anemia and as JKT said can be fatal.

You can wash the pups in soap or a dishwashing detergent to get rid of the fleas, fleas are resistant to water, but the soap coats them and drowns them.
If you wash them I would do so with a bucket of warm water next to the whelping box so that mum-dog can see everything that is happening and doesn't become stressed about her pups being taken away.
You will need to make sure you dry them THOROUGHLY, 2 weeks is the time when pups start the regulate their own body temperatures so you are on the cusp.
After bathing go through them with a flea comb to remove any dead (or live) fleas remaining.

You will also need to do the same to the mom and you will need to treat all of the bedding, the carpets and all rooms of the house.
When the pups are a bit older you can use commercial flea treatments but there isn't anything safe for a pup so young, using anything on the mother will be transferred to them as well.

I agree with Shaz's advise. You can use Revolution on nursing mothers, as well. It's a topical flea product that you can get from your vet.