If your 2 yr old is rough in any way, a puppy is probably not a good idea right now. While some puppies can tolerate roughhousing, unchecked abuse can lead to behavior problems. You also don't want to have an accidental skirmish between the two when your back is turned. If you don't think that you can trust your child to behave with the dog it would be unfair to the dog you bring it into your family.

Have you considered adopting an adult dog? Even the shelters ususally have an idea whether or not the dog was good with children. Consider checking with the breed rescues as well. Going to http://www.akc.org/breeds/rescue.cfm can point you in the right direction. The dogs are all evaluated for temperament (and you can see some of the child generated behavior problems in even the most common family dogs!) so you can be comfortable with your decisions. Contacting the rescue people can also provide you with more information: they know the breed problems better than anyone and are only interested in finding good homes for the dogs, not how much they can make selling them.

Good luck!