I'm new on here with guinea pigs, but have lots of experience with dogs, cats, bunnies and outdoor enclosures! One of my dogs could care less about our other animals, but the other is very eager to give them all some love and is crazy, hyper-focused on them. He thinks every living creature survives solely to be his best friend - one of our cats is actually his very best, rough-and-tumble friend after a very, very rocky start!
To get our dog to settle down around new bunnies, the new kitten (who's now 4 and his best bud), and now around the new guinea pigs, I first allowed him plenty of time around the cage while I was there to correct over-excited behavior. I'd keep visits short if the new animal was getting stressed as well - as stress and excitement decreased, visit duration increased. While we are hanging out, I'd spend time calmly talking to him and the new animal, letting him watch me interact with the other pet - trying to drill the idea into his head that these are new members of his family and nothing to get excited about. This is important - the dog being there wasn't about letting him check out the animal or have a meet and greet like a bonding session. It was about watching me interact with it and getting comfortable with its general presence in our home.
Equally important when it comes to training: I did NOT let him around the cage/in the room when I was not around. This is critical when training dogs: if they enjoy doing something naughty, it provides all the reward they need to do it again and makes it significantly more difficult to train it out of them!
Once he calms down enough that I can trust him to be in the same room as the pet without me, then I set up a folding dog gate around the cage (even our kitten was temporarily raised in a big cat kennel, with a perimeter!). The critical thing here, again, is to make sure he doesn't get the pleasure of being close enough to do anything stupid that he found thoroughly thrilling!
We are in this phase now with the guinea pigs. The dog can't get within 3 feet of the hutch unless I open the gate and let him approach with me. Outside the gate, the dog generally just watches quietly and naps - if the guinea pigs start talking or running around, he might sit up and whine a little bit... but he's also starting to get bored and spending less time at the gate; walking past it without giving it attention, which is exactly what I want. When inside the gate with me, I'm giving a him a bit more time and freedom to say hi, especially as the guinea pigs are now comfortable enough to approach the hutch wire and sniff noses with him, and I'm rewarding him for staying calm.
My dog has been through this drill a number times, so this does the trick, but when he was younger, I used a water bottle and sprayed him in the face when he got too excited - no verbal commands. It's the humane way to distract them and create a negative association with a behavior.
Patience and safety are key - don't move to the next phase too quickly. Create fully secure, temporary set-ups for each phase. Wait until they are totally calm for several days or a week in one phase before you move to the next. With an adult dog, I can get through it in 3-4 weeks. With a puppy, it will be months - and you will likely be more successful if you're also working on all-around puppy training.
Anyway - hopefully something here helps! It's pretty natural that the puppy is too interested to start off - research good training practices, enroll in puppy training, and keep at it for a bit. Keep the puppy on a leash, which is something I also did with our dog until I felt he was calm enough/old enough to trust that things wouldn't get out of hand and he would immediately follow my commands. If you have a trainer, then you'll also have that professional guidance to deal with your unique situation as it unfolds. Our dogs, cats and rabbits all get along great - to the extent that the dogs can go into the rabbit enclosure with me and they'll all calmly wander and say hi while I go about chores. Some dogs just want to eat all small critters, though - if you exhaust all training ideas and it still doesn't work out, then that's what you'll have to problem solve. I don't think you're there yet, though.
Regarding setup - I use the folding dog playpen for my enclosure fencing (come in various heights; just as good at keeping dogs out as keeping them in!). I zip-tie them to t-posts hammered into the ground. I found sandwiching a child safety gate between cinder blocks a great way to add an easy open, locking gate. I like that the setup is very solid and secure, nice looking, and fairly easy to take down or reconfigure. You could also skip the t-posts and baby gate - setting up just the folding enclosure takes seconds, as long as you think having it loose will be safe for your use. There are also lots of other grazing enclosures online to order or DIY. A semi-permanent enclosure could include some of the grassy area that would then also be protected from dog pee. Our enclosure doesn't have any grass, so I gated off a small section of lawn in the back corner as a no-dog zone so I can bring handfuls of grass to our babies, which they love!
Regarding the fall-out: The guides on this forum are very informative and have sections on bonding and fall-outs, including what to do with your now single piggies, or if re-bonding is an option. That might be a good place to start while you wait for a specific response on that. Those guides are playing a huge role in our evolving enclosure set-up.
. Now I am worried. I managed to secure them inside, but I think it is very unfair that they get less outdoor time just because we got a puppy. We live in Dubai and literally spend 6 months living in our garden, open doors and all. So far piggies were always with us loving the opportunity to get some fresh air. Is there any way to be able to have piggies out all day without needing to lock the dog away in the meantime? Like a wooden large crate with a lid or something? Has anyone hacked this? Is there even a way?
. Donuts ended up biting him a few days ago so that was the end of it. Very sad.
I think the balcony idea is absolutely doable.
! We feel a bit bad because obviously they were the kings of our household and had unlimited access to everything and tons of attention and now we are trying to find the way around it. It will be OK, it is just an adjustment period for everyone in the household I guess.
. Joke aside, we could never give up one of them. They are super attached to us and we to them. Donuts is like a little puppy that jumps on top of his house to get the cuddles, Buckets is way to gentle and shy to be able to get an owner that would not handle him carefully. But I agree, there is not much quality to life this way. Still better than living in a small cage not being loved or getting neglected I guess 
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