It's all in your view. I've been to WDW more times than I can remember, and this stuff just doesn't bother me. If a tour group dominates a ride, then it will be your turn next. I mean, we're talking about a matter of seconds or minutes. Tour groups are paying customers just like me, whether Brazilian, Asian, American or just a massive family meeting for a grand gathering. I'm sure you want to be able to enjoy the rides together with your group. Why shouldn't they?
Who cares if someone uses a
scooter? Like anywhere else, watch where you're going so you don't bump into someone or be prepared to jump out of the way if someone doesn't see you.
Line cutters? I honestly don't remember feeling like someone ever "cut" in front of me. If it's happened, it just didn't make a big enough impression on me to remember it months or years later. However, after reading these boards, some feel that if a woman and child are in front of them in a line and the dad joins them after a few minutes, that's cutting. If I'm in a line for an extra couple of minutes because of something like this, well, heck, this is more time for me to find a hidden mickey.
You'll have a wonderful time. Just concentrate on you and your family having fun, not why someone is in a scooter or a large group who wants to be able to go on Kali River Rapids in the same raft. You'll be in the next group.