While you can put limits on wild play between big and small dogs for safety its normal for an adult dog to push a pup around while it learns the rules of dog behavior.
http://www.the-puppy-dog-place.com/introducing-a-new-puppy.html
I'd plan supervised play and set up a space where everyone can see each other without interactions you can't control for times you can't supervise.
Puppies usually pester adult dogs unmercifully as they want play, they want attention, they want *somthing* interesting to happen. When they are under 4 months of age they may not have a good understanding of dog social signals of 'stop it right now' when the adult dogs do those behaviors. The pups learn the signals by being taught by the adult dogs. Baby pups get 'puppy license' to get away with some things but the adult dogs will correct them. With tinier pups you just have to make sure the adult corrections are not too hard.
Adult dogs familiar with many other dogs and that are socialized with their own species
typically set limits for behavior using a growl or snarl and may even pin the pup and make it squeal if its being rearlly rude. This is normal dog behavior and should be allowed. You stop it if the adult does not back off when the pup YIPES. Most dog interactions are quick and quickly forgiven. A STOP THAT dog response can be rapidly followed by OK now play nice and interactions continue.
Adult dogs that are not socialized well enough to know proper dog behavior with pups, or are known fighters, may use too much force which can harm a puppy. Because of risks to the pup you really shouldn't leave one alone with an adult dog until you're sure all is going well. With a toy breed that is a longer process than with a larger one where the pups are sturdier.
Make sure the adult dogs get some time away from the puppy getting your attention for play etc. No one likes to be the baby sitter all the time.
Things should improve as the pack works out who is who, how to play nice, and the pup learns some polite dog behaviors.
I'd suggest puppy kindergarten for the puppy and www.apdt.com may help you locate a puppy class to attend.
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics