I went last Friday night and had a great time. I can answer your questions based on that. We checked in at Poly. They handed us wristbands and a brochure, and said buses would start at 6:30. We headed out to the bus area at 6:31, and around 6:55 were told the first bus would not be until 7 PM. Shortly after 7 2 motorcoaches stopped to pick up people. There was quite a bit of traffic by the park with all the buses arriving and way more cars than I ever see there!
I would suggest checking in at your resort if you are staying at a DVC property, at least if you plan on arriving early. When we arrived at TL, it was a mass of bodies by the ticket booths, and the check-in tables were in the midst of the madness. If you already had your wristband they just moved you on into the park.
We rented a locker, but I would not do that if going again. You don't really need anything except an ID and your member card, and I put those in the waterproof neck pouch with my phone. We could have just left our shoes/clothes and personal towels on a chair. Got right in the lazy river after leaving stuff in locker and floated around that for a while - most crowded I have ever seen that!
Waits for tube rides were about 15 minutes. For the characters, there was no wait for Donald (maybe because he was towards the back of the park?) and about 10 minutes for Sebastian and Genie.
Maybe it was our timing when looking for snacks, but there was not much of a line at all. In addition to water and lemonade, they had the soda machines available and someone standing nearby with ice. So you could grab a cup from the beverage table, have the cast member fill it with ice and then get whatever you wanted from the machines.
We had a great time, and I would love to do it again. The one thing that surprised me the most was the parents with smaller kids. While hanging out in the pool, there were parents who tossed their kids into the waves as they approached and then grabbed them as the wave moved past. Just astounds me! And at either Mayday or Keelhaul Falls, can't remember which, a father told his small daughter she had to ride it by herself because those are the rules. She did not want to go on it at all, let alone by herself. And sure enough, when her tub got to the bottom of the slide it flipped over and she went under. Lifeguard had to go in after her. Poor guy had to go in twice in 5 minutes because of small kids. Just because the child is tall enough does not necessarily mean they should go on the ride! The signs say you should be a good swimmer!
I bet you're right about the lines, though. They're going to have to do something like volcano bay to make the waits more tolerable.
