I'm not sure what that surgery is, I'd have to look into it to see for sure but I'm sure it's fine, but it may not be necessary if you take a lot of precautions, our boy is black lab/great pyrenees and always been fine. I heard you're not supposed to let them eat or drink for an hour before and after exercise (i think hard but probably any) but ours always drinks after and is fine and usually eats not long after and is fine too but I would still do it especially since yours will get bigger.
Another thing is a good quality food, I can give you some good ones that are still reasonably priced if you want.
Also, another really important thing since he's already so old and missed the first fear period is to make sure you socialize, socialize, socialize. The second fear period I think should be coming up so I think you still have time. Just try to have as many positive experiences. Now from the looks of it, with the goats and everything, it seems like you may be out in the country, in which case you may not encounter many people, but I would still try to socialize as much as possible. If you can, have people over or take him to lots of stores/in town, etc. However, even if you can't meet many people, you can still socialize. Have him meet dogs, have him on as many different surfaces as possible (such as like dirt, gravel, grass, concrete, tile hardwood, etc. Etc.), make lots of noise (in his time, don't traumatize him), smells, sounds, etc. Strange things like canes or walkers or skateboards, etc., whatever you have. The idea is just to introduce him to as many different strange and new and potentially "scary" things as you possibly can so then when he encounters something he hasn't seen before, it's not so scary and he's confident and not scared or aggressive. Some Saints, and even sadly some lines of Labs and Goldens, can be aggressive and even if he never becomes aggressive, he is still a very large potentially exuberant dog so this is really important. That and training. Speaking of exuberance and training, I'd teach impulse control. With mine I play the "wait" game, I put food down, low value at first and not for very long, and say wait. if they leave it alone, they get to "take it." I start with it far from them, low value, and for a really short time, then go for longer and/or closer to them, and eventually increase the value of the reward, etc. Now I can out food down all around him or even just one piece of meat and my dog won't touch it for quite a while. Sometimes he slips, we're still working on duration, but it helps. I also make him sit before we go out for walks and food, and when we go out to go to tge bathroom, he will stand and wait on the deck or behind the door threshold until I put the rope on (he runs off so he also has a long rope for outside even if we don't go on a walk). I can even grab his collar and walk him to the leash or to the house if somebody left it away from the door or I shut the door, go get it, and bring it back. He even stops and stands on walks if I way "wait" or "stop." Sometimes I have to say it more than once or if I'm behind and move up, he'll go again and I'll grab his harness or collar and repeat, but usually he's excellent and once I repeat or grab him he won't move. Just little things like this help. It took a lot of work to get him to be so good at waiting and impulse control but it's worth it. He still loses his mind at guests ir when his favorite family members come home but that's to be expected as they encourage it and we rarely have guests.
Anyway, I guess I kind of rambled there, sorry, but anyway...
Another really, really important thing is please DO NOT get him fixed too early. With the ACD you may have to but most vets usually say the 5 or 6 months thing and ours I think we even got done at 4 because he was "plenty big enough" but that's actually really bad. It's bad enough for smaller dogs but it's really detrimental to bigger dogs. Especially males. There's loads of new research that's been coming out that recommends to wait until at least 16-18 months, sometimes even 24 months. Larger dogs are not done growing until at least then and if you do it too soon it can mess up their bones and joints and everything. They no longer have anything regulating growth and saying to stop growing so they'll keep growing and the leg bones can become too straight, you risk leg injuries, etc. Etc. I forget the exact problems but I could probably find the article and I do remember that dogs fixed too early have a much higher rate of leg injuries and I think ACL or just general tendon or ligament tears, etc. And I believe it because ours has torn a tendon or ligament and still sometimes has problems with that leg if he goes on sand or mud, etc., he'll limp. Now, he has a bad hip already genetically but still. There's a lot of issues. Some people don't even get their dogs fixed if they can properly control them. Just a thought. But of course don't feel bad if you have to do it sooner but I would just wait as long as possible to do it. Sometimes with females they even do ovary sparing surgery now where they keep the ovaries so they still get the hormones but for males I don't think that's possible as the testes are what provides both the hormones and the sperm. Plus it's kind of an out there idea anyway.
Anyway, your dog is really cute.
And back to the bloat thing, I don't think special surgery is necessarily needed as long as you take all of the precautions.
And I'd also recommend a slo-bowl. They have boring ones but I think mine the actual name is Slo-Bowl and I think it's by Kyjen or something. There's 4 types, I have the flower and drop, wouldn't recommend coral as spaces are small for large dogs, hills is okay, flower and drop are the best imo, and anyway, it basically makes them not just eat slower but it's also a game, chasing the food all through the "maze". I've heard plenty of dogs don't even like regular bowls after. It's fun, fairly cheap, and helps them eat slower.
I'd also recommend some puzzle toys, I have a bunch that we use that I can recommend if you want. Those are really fun as well as great mental stimulation as well as, obviously, making him eat slower.
You can also train with the kibble or put it in a Kong or some sort of chew toy and that will also help them eat slower and be trained.
And another thing I do is I hide food all around a room and tell them to "find it." great way to use their nose (mental stimulation) and eat slow. You may want to use something higher value first though and also don't start with the food all around right away, start with a few easy to find pieces right in front of him, and say something like "find it" or "seek" then you can slowly make the game harder and with more pieces until you can hide it all over the room. I often use pieces of meat, cheese, dog treats, etc. In addition to or instead of kibble. Something somewhat smelly really helps as well so they can smell them out.
All of these ideas, especially the "find it" game, puzzle toys, and training, will also be great mental stimulation for your ACD as well and, perhaps with supervision at first to make sure neither gets too rambunctious or food aggressive, would be great thing for your children to do with the dogs too.
Tiny is adorable though and cute name.