For some it is extremely magical. However having some knowledge that even the most magical trip has it low points will help you. A good example of too high expectations is the restaurant Boma and Zebra Domes. You will hear a lot of people complain that they were disappointed with Boma because of all of the hype, and they had just expected too much and no restaurant could have lived up to those expectations. While I loved Boma, I was nonplussed with the Zebra Domes. The way people go on about them, you'd think they were literally the best dessert in the entire world. They are ok in my book, but that's all.
I think the planning you have done will help you to have more real expectations versus someone who just goes for the first time with no idea what to expect. Guess what, you won't love every ride. You won't think every meal you have is the best ever. You may meet some guests who definitely can't find the magic. You may meet a CM who is in the same boat as those guests.
That is ok. The great thing about WDW is there is something for everyone. And don't to sweat the small stuff.
A few first trip mistakes you can avoid are:
1. Don't be a commando all of the time you are there. Stop and smell the roses and see the magic in the little things.
2. Listen to your body, and those of your family. If your body says hey I need a rest, then give it one. If it doesn't, give it one midday anyway.
3. Go to the parks early at least some of the time to get some stuff done and then relax in the afternoon.
4. Remember that you can come back and see the stuff you miss on your next trip.
If you haven't bought any guide books I'd suggest PassPorter and The Unofficial Guide. They make nice companions.
Most of all have fun.
Mel