Looks like a Mallard and a Pekin to me. The one that looks like a Mallard could be a Rouen too. I am not the best at telling those two apart. Usually rouens have two lines over there eyes and Mallards 1, but it is not always 100% accurate.
For sexing, the only way to do it at that age is vent sexing. That can be difficult to do accurate and safely not hurting them. Otherwise, you have to wait till their voices change which can take up to 10 weeks of age. After that, they molt into their adult plumage about 12-13 growing the tail curl and possible drake colors depending on the breed.