we have been there during cheer competitions, and here's what we saw about cheer teams affecting lines in parks: they didn't. The most we ever saw get in line at one ride at one time was maybe 10 kids. We did not hear any cheering inside the parks from cheer groups, though someone with a toddler in a stroller told us they were staying at a resort that had a lot of competitors and she said the kids were outside practicing at all hours (to the point they called the front desk to complain when practice was going on well after 10 PM next to a building...said it was so loud they woke up the baby.) But as far as big groups of kids getting in line at the parks, we didn't see it (or hear it) They didn't seem to be traveling the park in huge groups. There was far less affect on stand-by lines than the South American tour groups that have 150-200 kids all get in line at once.
In fact, we only saw a big group of cheer kids one time, and it was one of the funniest sight we ever saw. There was a big group of teen-aged girls all wearing the team warm-up suits, each with matching back-pack, all made-up and hair perfect...using the back-packs for pillows, and draped over ever horizontal surface in Fantasyland, SOUND ASLEEP at the Magic Kingdom. The happiest place on earth, and they're sleeping through it, lol. I chatted with one of the moms and she said they had been up at 4 AM to get on the buses from their resort to WWOS for a very early competition...then they had this 10 AM-4 PM break to either go back to the hotel & sleep, stay and watch other competitions, or go to the park. All the girls really, really wanted to go to the park. She said they had gone on one ride, and then crashed. There must have been 50 of them sound asleep right in the midst of all the crowds & noise of the park. The mom said it was the most expensive nap her daughter ever took, lol.