I definitely concur with Tom! Speak with your veterinarian about what is appropriate for your puppy in your area. Because the diseases these vaccines prevent are potentially devastating, and sometimes fatal, it is very important to make sure your new family member is protected. Tiny dogs sometimes may not feel good for a couple of days after receiving vaccinations, so talk to your veterinarian about splitting them up: he can get a a DHPP one week, and then the lepto another week--if indicated in your area, and his rabies at another time. That way his system won't be so overwhelmed at one time and he'll still get the protection he needs. And, as Tom said, heartworm prevention is imperative in your area! Good luck with your new puppy!
How exciting for you to have a new little puppy at home!!
When you refer to the "7 in 1" and "5 in 1" vaccines, you are really referring to the types of diseases that the 1 vaccine helps to prevent.
In both cases, the most common antigens in these vaccines are Canine distemper, canine parvovirus, canine adenovirus (which cross protects against canine hepatitis) and parainfluenza. The additional 2 in the "7 in 1" vaccine are usually 2 strains of leptospirosis.
The leptospirosis vaccine is actually created from bacteria (and should actually be called a bacterin). The cell wall componenets of these bacteria can cause reactions in some dogs that can be quite severe. Fortunately, most of the newer vaccines are generated without using cell wall extracts to help minimize these adverse reactions. Some veterinarians and some dog owners believe that smaller dogs are over-represented by these reactions.
The best course of action for you is to have a discussion with your veterinarian about the risks and benefits of the added leptospirosis protection. I live in the Midwest instead of the South like you do, so I am unaware of the prevalence of lepto in your area. But, I can tell you that lepto is a concern because it can spread to people as well.
If you have not already taken your puppy to your veterinarian, now would be a great time to do so. Not only can you discuss vaccination schedules and type of vaccines, you can also get the puppy started on heartworm preventive (a big problem in your area) and strategically deworm the puppy for roundworms and hookworms (both of which can spread to you and your family).
Please let us know if you have any follow up concerns. Good luck!!