That family photo is amazing. Your doe looks very pleased with herself and what colorful babies! Congratulations on your kidding! It sounds like you did great. Let me try to address some of your questions, and I'm sure others will chime in too.
I hope some of that helps! I'm sure some of our much more knowledgable folks will chime in also.
- If the placenta is hanging out and wrapped around a leg etc. Can you trim it or should you literally just leave it be. Don't touch it. It'll be okay. The doe moving around and the contractions of the uterus caused by the kids starting to nurse will help her pass it. I've never seen one that needed assistance once the doe started passing it.
- Anything else I should do for the scours at this point or just continue monitoring? Is it actual scouring or just atypical poops that look like a dog's poop or a log of semi-formed berries? It is EXTREMELY typical for some does to have atypical poops after kidding, sometimes even for up to a week. The change in diet with lots of added grain can also cause this. Unless it is actual watery scour, I would not be concerned. Monitor her rectal temperature to ensure that it's normal and keep making sure she's eating and drinking. Vaginal discharge is totally normal but please make sure it's not discolored or malodorous.
- As for the kids, it's so hard to know if they are getting enough. We are concerned that this doe may not produce enough milk to support triplets, especially once they start to grow and need more with each meal. Should we be making the executive decision to switch one to a bottle now? Can we try to "cross train" one on a bottle once they are off colostrum so they are willing to take it either way? Weigh them. It's the only way to know. At this age, if you're concerned she may not be making enough milk, watch them to make sure all three are feeding frequently and weigh them several times a day. If they're not gaining good ground or you see a loss, you can indeed pull one to exclusively bottle feed or you can supplement one or all three with bottles or a lambbar. Buy a hanging fish scale with gram weights and a lamb sling for ease of weighing - Tractor Supply and farm supply stores will usually be able to supply what you need. You can also just put the babies in a tote bag at this age and hang it from the fish scale.
- We have read that bucks need to be separated around 10 weeks due to risks of them maturing sexually, which seems pretty early to be weaning off of milk. Would bottle feeding the buck make the most sense then so we can continue to give milk after separating? Depends on what you're doing with the buck. You can wether him at any point and then obviously he can stay on the dam until he is sold or she weans him. If he is to be sold for breeding, or if you prefer to wait longer to wether him for urinary health, he can stay on the dam longer if you utilize a buck apron. We get ours from Bacchus Johnson Aprons. Either way, 10 weeks will be fine to get him off milk if you must separate him at that point. Most people will wean between 8-12 weeks.
- Our other doe is likely going to pop imminently but we arent sure what to do with the birthing area. We feel that the first doe needs to stay in there for now but aren't sure it's a good idea to bring the other doe into the same area to deliver. We are actively working on a way to partition the box stall but just wondering if anyone has any thoughts on this. My opinion is don't bring another doe into the postpartum area with these guys still in there. There may be conflicts and anxiety. Best bet is to contrive a partition - perhaps you can grab some pallets to achieve this. We keep pallets on hand if we need to create temporary multiple stalls in our big winter kidding pen. But if the kids are sufficiently mobile, you can really put them back with the herd anytime. We put our dams and kids back with the herd when they're 2-5 days old as long as everyone is up and around. Once the babies are dry they are extremely cold hardy and they will enjoy starting to learn to run and jump.
I hope some of that helps! I'm sure some of our much more knowledgable folks will chime in also.