A couple of years ago I had myself worked up into quite a frenzy reading these boards with the dire predictions of how busy it would be the last week of June. Granted, it wasn't the opening of Carsland/Remodeled DCA, but it was the summer of the Nighttastic promotion with the new dragon in Fantasmic, etc. And then again last summer with the Star Tours/Little Mermaid openings. But I was surprised over and over how much we got done first thing in the mornings, and how much a positive, relaxed attitude had to do with it.
Is it crowded in summer? Yes. But knowledge is power, and if you do wise touring (go early, go early, go early) you will be pleasantly surprised at how much fun you will have. The grand majority of people are not active on these boards, and SO many people sleep in on vacation, even to
Disneyland. I have friends who go every summer and have never ever used their magic morning, always come to the parks around noon, rarely use fastpasses, etc. I think they are more of the typical park-goer than what you see on here.
As long as you don't set your expectations too high and enjoy being there with your family, you will have loads of fun and start planning a return trip soon after you leave (or even before you leave!)