I've been a Type 1 for almost 30 years and have never had a problem with bringing the necesaries (insulin, needles, meter, lancets, etc.) into the parks. Security is always helpful and courteous. A guard at the Epcot bagcheck two weeks ago even showed me his meter that checks him constantly and told me where to look for it online (haven't yet).
As for insulin, Cheshire Figment's advice is perfect (btw-thanks for the link Cheshire Figment to the coolerconcept site - I've had a hard time finding the right cooler packs). I use a Humolog pen w/o any cooling pack and I've been fine, even in the August heat last week and the week before. Insulin will be stable at room temp. I just keep it in the backpack and out of the sun. I'm risking it, I know - but I'm going to check out that link!
Learn from my mistake - make sure you have glucose tabs or a juice box w/ you. I thought they were in the backpack last week, but much to my surprise they weren't there when I had a big drop.