I think you'd be fine without it! Your trip falls in the middle of the week and you have three whole days to experience the park. When DH and I go, we often do Tuesday - Thursday and get to see everything several times and more.
One thing that Ridemax doesn't do is allow the option to select nighttime-only as an option for rides. Several rides in particular, the Matterhorn and Big Thunder Mountain Railroad, are worth riding again at night because of the park views and because how the darkness changes the ride. With the Matterhorn, you get to see the park lit up like a dream. With BTMR, riding at night means your eyes have already adjusted to the darkness and with that, the colors and visuals in the caverns are brighter and easier to see. Plus the darkness make BTMR's twists and turns exciting!
So, I completely digressed but with Ridemax, you can't select "nighttime only" as an option for rides, which I consider a flaw in the design. If you were going on peak days and had limited time, then it's a great tool. But judging by your schedule, you'll have plenty of time to do everything...and then some!