Your flight times are perfect.
You can reserve days and times for your shows in advance, if you'd like. When it's show time, they let the folks in first who have reservations. Then ten minutes before the start of the show, they open the doors to everyone, assuming there's still space left.
As for dining in the dining room, you can request Main Seating or Late Seating in advance, or you can opt for Anytime seating. If you do Main or Late, your dining time is the same every evening, at the same table with the same people. That is, of course, for the nights you eat in the dining room. There are many other places to eat dinner, some which are included in your price, and some of which charge a surcharge.
If you do Anytime dining, you can show up at the dining room any time you want, and be seated in turn. There may be a short wait if you get there at the more popular dinner times. If you're willing to sit at a table with other people, your wait won't be as long as if you request a table for 2. Or, you can make a reservation in the dining room if you know earlier in the day what time you think you'll want to eat that evening.
it sounds complicated, but it's not. You'll get the hang of it very quickly. It's just that the Oasis offers so much in the way of choice of dining spots, but you'll find your favorites quickly.