From the Disney Wide World of Sports Schedule:
April 25th BASS Federation Championships
Welcome to the World Championship of Amateur Bass Fishing featuring the top 15 anglers who succeeded in their quest of a grueling qualification process that began with 50,000 anglers. These anglers represent the top BASS Federation fishermen from 46 State BASS Federations, the District of Columbia, and 6 International BASS Federations in Japan, South Africa, Zimbabwe, Italy, Mexico, and Ontario, Canada. Competition also includes the returning 2004 Federation Champion and the Paralyzed Veterans of America Bass Trail Grand National Champion. Five of these amateur anglers will qualify to compete in the 2005 BASSMASTER Classic. This event also includes the National Semi-finals of the BASSMASTER CastingKids Program. 96 children, age 7 - 14 will compete for 10 slots in the CastingKids Championship held in conjunction with the BASSMASTER Classic. Also in attendance are the Presidents and Conservation Directors of the 53 BASS Federations for week-long meetings.
April 30th Walt Disney World® Inline Marathon
It's not an ordinary day when you can put on your inline skates and zip down Hollywood Boulevard, coast along the Eastern Seaboard, and travel through eleven countries all in one morning. But then nothing about the Walt Disney World® Inline Marathon Weekend is ordinary! So pack up your skates and your family and join us for a magical skate around the World.
April 30th All Star Kids' Classic
The All Star Kids Classic is an exciting opportunity for children ages 3-12 to be a part of the 2005 Walt Disney World® Inline Marathon Weekend
and also many schools are there for Magic Music Days/playing at Disney. I know my niece's school is the 28th and with her there are 7 additional family members going (me among them

) Using this weeks bands schedule as a guide, there are over 200 performances at the Magic Kingdom alone (keep in mind some schools send several band/orchestra/dance/choral groups so it's not just "a band" coming). Then there are some at EPCOT and some at Downtown Disney--whew!!! the numbers are staggering! (Although some bands/groups perform in more than one spot I think)
So yes I think the parks may be a bit more crowded than originally anticipated. While participants in these events need to be at the event (and more than likely their family will be there cheering them on) I am sure most of them will do a few days at the parks around the event. (For instance--all of the groups from my niece's schools are leaving WED, performing Thursday, and then spending Fri & Sat at the parks, heading home Sun). I am having a very hard time getting reservations for PS's and now we want to get/share an Illuminations Cruise and I can't find one (obviously). However we do have CRT for Saturday morning so all is not lost. (Which I would gladly give up for an Illuminations cruise as I just found out that I'm the only one who really cares about it and I've done it before)
Just my $.02 worth.