I used RideMax to help plan our trip in April. I have also used the guides in the Unofficial Guide at all our past trips to WDW. I think that if you are going at a time of year when crowds are an issue, and it sounds like you are, a plan to follow can help make sure everyone in your group has the chance to see what is important to them. It also gets rid of that overwhelming feeling that can happen with large crowds. That being said, you want to always remain flexable. I also look at the plans and whatever rides are put very early or very late I try to stick to, because we don't like mid-day lines at the big attractions. We follow the plan and keep up a fast pace for the first two hours or so and then chill a little. I will also add in our favorite rides at least twice, so if there is a hitch we have back-up. I always say though, if you get there and the crowd is mellow, don't worry about rushing from place to place.
A huge plus on RideMax...we followed their EE plan and we had been on every open ride in Fantasy Land and were in line for IASW when it opened. We were in line for our second ride on the Matterhorn before there was any sign of a crowd filling the park.