You got some good advice but just to help you out in knowing what to expect I'll walk you through the weekend.
Your first major stop will be the expo. If you are already on property they will have busses from the resort to the expo. Do note where they are picking up because it will likely be near there where they will pick up for the races.
The expos are normally very large over at WWOS. For marathon weekend stuff was in 4-5 different buildings (bib pickup in one, kids bibs another, merchendise in another, etc). It can be overwhelming. When you get there first look for packet pickup. Should be signs but if not there will be people you can ask for directions. At pickup if you did not bring your signed waivor they will have a place where you can put in your information adn it will print a waivor for you to sign. Normally I don't find the lines long for this but you can always bring it pre-signed and skip this part. Then you'll go into the bib pickup room with booths all over the place. They will be grouped by race and separate booths for the challenges. Find your bib number on the waivor, locate the booths for your race, and head to the right line. Since you are doing the 5k and 10k which isn't a challenge you'll need to pickup separate bibs for both. After you get the bib you'll get funneled to another area to pick up your t-shirt again grouped by race and size. Finally after all that you are done with part 1.
After you get your bibs you can head over to the merchendise building and look at all the venders that are there. There will also be a separate section for "official merchendise" and those lines can be quite long. When I got my stuff marathon weekend the line just to get in was halfway accrosss a soccer field. I passed. Sometimes they will have character photos out there. Two years ago got a BB8 photo at the expo (yet another building). I don't spend that long at the expo but you could spend quite a while.
When you get back to your resort they should have a sign or something about race transportation. Take a look and make sure you know where the bus will be and what times start and finish the busses will run. This will be in other material as well but I like to double-check so I know for sure. The other thing I like to do the night before the race is have my race clothes already laid out so I don't have to think in the morning
On race morning, give yourself plenty of time. Getting up at 2-3am in the morning sucks but it is the reality of rundisney. Since you noted when buses start and end, do not wait and try to get on the very last bus. Go on and get down and grab an earlier bus especially since this is your first time and it can be overwhelming so you don't want to be rushing. Can also help with character shots too. You'll likely see a bunch of other people going so follow along. They normally have buses running almost constantly in the morning to the start line. Fill one up, it leaves and another is right behind.
When you get to the festival area you'll have to go through security and bag search. If you can avoid bringing a bag, do. It will save tons of time. At the festival area there will be a stage and video board and they will have stuff going on there. What exactly varies from race to race. You'll also have bag check if you brought gear you want to check. There will also be charcter pic opportunities most likely and those lines can get long quickly so if you want some get there early. This time before the race can get very boring. It just is.
About an hour before start time they will open corrals. Again since it's your first race I'd go on in shortly after they open so you have plenty of time to find your corral and so forth. I don't remember it being the case for dark side, but sometimes it can be a hike from the festival area to the start line. Once your find your corral you wait.. again. They will have some TVs and stuff up around the coral area but it is mostly just a waiting game till it is your time to start.
I think most people have covered the during race part. I would reccoment having a GPS watch or app or your phone to track your pace and make sure that including photo stops you stay under 16. Do that and you know you'll be fine and you have some buffer since the 16 minutes start from the last person but if you start under 16 you 100% know you are good. Go out and enjoy the race and have a lot of fun. Pretty much all the photo spots will have a CM who will take a pic with your phone and a photopass person. A few may just have a CM taking pics with your phone.
After the finish you'll go through the chute, get your medal, pick up a food box, some water, maybe a towel or mylar blanket (depending on weather), then you'll hit a section where a photopass person can take a picture if you want it in front of a backdrop that will have the race name on it.
After you get past those you'll get to family reunion area. If you are meeting somebody after the race pick a place to meet in advance. The 10k is a little harder to do that since you end at a dfiffetent spot then you start but you can guarantee they will have signs with letters on them (like A-D, E-H, etc) so pick a letter in advance and agree to meet there. The character stops from teh start of the race will be here at the end so you can get character pics here too if you want. Not much else going on at finish so after you find your people, find your bus and head back to the resort.
So that is a longer message then I planned to type but covers what to expect for the races. As for places to watch, cannot really answer that until the course maps come out. Hope that gives you an area what to expect.