I'm so glad your questioning the safety of doing vaccines for your little one.....It never ceases to amaze me how clueless vets are in this important area of care for pets.....
To answer your question it is NEVER a good idea to get more than one vaccine in a visit. It overwhelms the pets system and greatly increases the risks for undesirable adverse reactions, especially in smaller dogs. The shots should ALWAYS be spaced 3 to 4 weeks apart, 4 weeks is better. If you give a shot as close as two weeks apart the first shot will block the second one from "taking".
From all my reading a pet should NEVER be given a combo vaccine, it greatly increases long term health problems and exposes your pet to vaccines that are not needed or beneficial to the pet.....and booster are unnecessary and put your pet at risk for long term health problems.......
This is from this site on vaccines:
Vaccinating Dogs: What Your Vet Hasn't Told You
Melissa Kennedy, DVM, PhD, DACVIM wrote in DVM360 on-line magazine: "The likelihood of adverse reactions in dogs has been found to correlate with the size of the dog and the number of inoculations given, with higher risk associated with small size and multiple inoculations." This means: no combo shots for small dogs -- or any other dogs for that matter. And NEVER GIVE ANY OTHER SHOT WITH A RABIES SHOT. Wait at least three or four weeks between the rabies shot and other shots.