When you have a small puppy, you definitely want them to feel comfortable. It is totally normal for them to growl or snap when they're feeling overwhelmed and unsafe, but your goal is to try to avoid that happening. Step in and give the older dog a time out when you see your pup start to look uncomfortable (shrinking back, trying to get away, flattening ears, rolling on his back - all of these are clear 'stop this is too much' signs). Get the dogs used to each other through a barrier, like a baby gate. Avoid them fixating on each other by having each of you (the humans) playing with your respective dogs on either side of the barrier, so the dogs can see each other but they're more focused on the play. Give them calming activities in this setup like a nice chew to gnaw on or a stuffed food toy like the Kong Classic each so they become used to being calm in each other's presence. When your pup is a little older, walk them together so that they're used to being in a group but the environment is too interesting for them to hyperfixate on one another and get too amped up. At first you may have to walk far enough apart that they can't have physical contact while on leash.
The doodle is in a tough age where they're starting adolescence. A lot of dogs are A Lot during this time, and not very good at self-regulating excitement or manners. Set yourself up for success by making sure he's had exercise and mental stimulation that day before he interacts with your puppy, and keep their interactions short and try to end them before your pup gets overwhelmed.
There's some great socialization classes out there, but there's also ones that basically turn into puppy fight club. Look for one that focuses on introducing dogs to different sights, sounds, and experiences and just kind of hanging out around other dogs, and any free play is done in very controlled, careful ways. My trainer will section off the training area and have two puppies of similar size and energy level play at a time, only working up to three or four and/or multiple play sessions happening at the same time once she knew every puppy well and had spent time talking to us about how to keep play sessions positive and interrupt overexcited or bullying behaviors. Run from a 'socialization' class that's just throwing a half dozen or more puppies together at once the first day and letting them 'work things out'. You're risking creating anxiety, even fear aggression, around other dogs or a bully who doesn't respect other dogs' social signals.
