Hi! I am yet another planner... must be a symptom of being a Disney fanatic. And I have to say I agree w/ everyone who says planning is half of the fun - maybe even more!

When my DH & I took our DD's last may, my MIL went with us as well, and she teased me for all the planning I had done. I wasn't obsessive about it, but just had a general idea of what park to hit each day, where our ADR's were and lots of tips I'd learned from I'cot about where to be and when in order to get around the rides and parks most easily. Well, two days in and she was loving all the planning I'd done... mostly b/c the sense of urgency was gone - we knew what we wanted to see, we knew what we were willing to miss, and we managed to do most of what we'd wanted to do without having to run around like crazy.

I think Disney is the perfect vacation for planners - it gives us the chance to enjoy our vacation before we even leave, and I think it totally reduces the stress when you're there, as well. Like others have said, being flexible is the key - kids get tired just when you least expect it, or else they dislike an attraction you think they'll love - as long as you're willing to miss a few things, or re-arrange your plans a bit, you'll be fine.

And just a tip re: kids and getting separated - that was one of my biggest fears, too - each day, I took a small piece of fabric tape and wrote my DH's and my cell phone #'s on it and put it below the tag of their shirt, on the inside. They knew to tell a CM where the number was in case they got separated from us, and we would be just a phone call away.
I've heard lots of other ideas similar to that - I'm sure if you search the boards, you'll find lots of good ones!

Good luck, enjoy the planning, and have a GREAT trip!!