You have two senior dogs that you failed to socialize. It's unfair to expect them to get on with an energetic and obnoxious puppy. That would be like leaving an ill-mannered toddler with an elderly person who has never been around children and expecting them to tolerate and enjoy being screamed at, hit, bitten, and constantly pestered.
You should not have brought home another dog until after spending plenty of time socializing your older dogs with other dogs, particularly those that are more energetic than they are. And then the initial introduction should have been done on neutral territory so they saw the new dog as aless of a threat (such as a friend's yard). But, it's too late for either of these things to be done now.
About all you can do is to monitor the interactions to make sure none of the dogs get hurt, and the puppy is not harassing the older dogs. When the older dogs express that they aren't interested in interacting (by growling), the puppy should back off and leave them be. If it does not, you need to remove the puppy from the situation at that time and not allow it to harass the older dogs. Until the puppy is older and more sedate, it's unlikely your older chihuahuas will have any interest in interacting with it. It was quite unwise to bring a puppy into a home with two unsocialized senior dogs and expect it to work out.