Regardless of when the kids were little, up to when they're (now) teenagers, we take a middday break. The heat can get pretty intense, the crowds, the intangibles that make you say "eh, let's come back later," grab a bus and head back to the hotel.
We were complete noobs when we visited WDW the first time in '01, took our kids (5 and 3), and tried to make a full-day of it, and it was disastrous. Kids were tired, hot, cranky, and I thought I'd lost my mind for having driven them 1500 miles for a miserable vacation. Fortunately, cooler heads (my wife) prevailed, she suggested a break back at the hotel, which we did, and we went back that afternoon and had a great evening. For the rest of our week, we took an 11AM-Noonish break every day for about an hour, and we had an awesome rest-of-the-week.