I find that sometimes the guidebooks and/or experts are helpful, and sometimes they're not. It depends on your family.
Yes, every expert everywhere recommends arriving early and taking a midday break. There's very good reasons for that (crowds, heat, etc.). We've never done it that way. First, we're not morning people, and second, we're from the west coast, so getting up early on east coast time just isn't going to happen. We arrive late (say, lunch time) and stay late. The parks tend to empty out after dinner, and it lets us keep our internal clocks in a familiar rhythm. It works great for us, but some people would hate it. Knowing your family is more important than any advice.
The property is huge, so even hotels just outside the park boundaries take significant driving. If your kids get overstimulated or need down time, by all means, do it. Otherwise, it will just start to feel like a hassle. We have friends who planned on hitting multiple Disney parks in a day, plus hotel pool breaks, and they were so exhausted by all the between park travel that they've vowed never to come back, and their kids are far past the nap stage. We never plan on more than 2 parks in a day. Disney transportation is free and varied (buses, monorail, ferries), but it will take a minimum of half an hour to get from one place to another, because the property is so immense (roughly the same square miles as the city of San Francisco).
Have fun! We love Disney World. I'm jealous. :)