Relax....You're gonna have a great time and take some great pictures!!!
Lenses. re: lens, it depends on what you are shooting. Are you going to the parks primarily to indulge your photography hobby (where you would want specialized lenses)?
Sounds more like a family vacation, in which case I would recommend the 28-135. Great for a variety of needs, versatile.
Camera Bags. As for fearing you may break the camera, you may want to invest in a bag that isn't so big that you'd bring ALL your gear in (and hence, too big to comfortably lug around). Something that fits and pads your camera and one lens comfortably.
I bought a Tamrac Velocity 6 for my recent WDW trip, where I only wanted to carry around the camera and one lens. Worked well, but I think it would be too small for your 40D (fit my XT VERY snugly). Here's a picture of the Express 6.
They do make bigger sizes, and you can test it out at your local Ritz or Circuit City. You may want to try a Velocity 7, which is more of a sling style:
My Express 6 is a very nice tan suede color.
Accessories. You may want to bring a different card for each day, so you can leave the others in your room w/o fear of losing them, etc. You may want a monopod/gorilla pod/etc. for certain parks, certain situations.
If you are going multiple days, consider not bringing the camera each day. On my recent 5 day trip, I left the camera home one day. It was nice not having to lug it or worry about it, but I did miss it just a little bit...
ALSO, remember, each park has lockers, so that is always an option should you want to store it away for a little while. I brought my monopod for Fantasmic pictures, but kept it in a locker all day until I needed it that night at MGM.
HTH! Have a great trip and bring back pictures to share!
