We have three young children and on our last trip the oldest was 4 and the twins had just turned 2. We were there between Christmas and New Years and we knew the crowds would be pretty large so we got 5 day Park Hoppers because we thought we would need extra time. Like you, our two youngest were free because they were under three. If you think it will be busy I think you should go for it and get the 5 day Park Hoppers. They never expire so if you were tired after day four, it's not like they will go to waste. Touring with children can slow you down so you may need the extra day to make up for that. From what I understand from other people on this board, most people take a break in the middle of the day. We didn't really do that. We got there when the parks opened and rode everything that was a "must see" at least once, very often twice, prior to 11 am. As it started getting busy, we used Fast Pass a lot. Around 12:30-1:00 we would have lunch. In MK there is a fairly large place in Tomorrow Land where you could get chicken tenders, burgers, hot dogs, french fries... It was out of the sun and fairly cool in there. Sorry, I can't remember the name. We took our time with lunch, rested and revived ourselves. We did a few more rides and then found a spot to sit and wait for the parade. The parades were one of our favorite things to do at the parks. We didn't do character breakfasts or autograph books so this was our kids' big chance to see the characters and they were thrilled. The Stars and Motorcars parade at MGM often gets a bad rap, but that was my favorite. It is all characters. The MK parade stops along the route and kids get called out to interact with the characters. That was a thrill for my oldest. At AK the characters come around during the parade and shake hands with the kids and high five them as they walk the parade route. It was fantastic! After the parade, we would do a few more rides and then head back to the hotel for a swim, dinner and bed. We were offsite and found once we got back to our room it was hard to go back to the parks at night, especially with the kids. We did go back twice though. The kids fell asleep in their strollers and it was really a treat for my DH and me to have some "quiet" time strolling around the parks and taking in Disney magic. Another suggestion would be to visit MGM to be in the middle of your touring plan. There are a lot of shows and it will give your feet a break. Animal Kingdom is also a great park to do in the middle because you can really do it at your own pace and really take it in. Those two parks don't seem to be as crazy as MK. We did do MK three out of the five days though. We didn't do Epcot during the day, only at night so I can't give advice on that one. I do have to admit though, once my kids went to MK, that is all they wanted to do. They were ok with going to other parks as long as they knew the next day would be a MK day. We also had to explain that all of the parks were park of Mickey's Disney and that it was important to see all of it.
Good Luck.
