I'll be there at about the same time as you, with my almost-7-year old and 1.5 year old. Last time I took them, the two things that helped most were 1) Getting to the parks before they opened (even if it was really early) to take advantage of that magical time in the morning when the crowds are lightest. I took my toddler on 4 Fantasyland rides inside of an hour, and it was great. 2) Reserving a table for a character meal. I like Minnie's Breakfast at the Plaza because you get to see tons of characters (there were 10 when we went!), and they visit your table and interact with the kids while you have breakfast, so you don't have to wait in lines to meet each of them. My oldest loved collecting their autographs in his book, and I loved eating Mickey waffles instead of waiting in 10 character lines.
I also recommend making the reservation for as late as possible so that you have as much time for attractions as possible during those lighter-traffic hours, before sitting down for brunch. I think Minnie's latest breakfast seating is 10:40.
I haven't used Maxpass yet, but from all I've read, I'm definitely springing for it. I don't know if your 5-year-old likes the big rides, but my oldest lives for them, and without Fastpass, we wouldn't get to do as many. It sounds like Maxpass makes the whole process even better.
And I second the Jedi Training suggestion! It's awesome. If you decide to do this, go straight there in the morning to register, or it will book up.
The midday breaks are key. It's true that it's no fun to leave and come back, but I think the biggest mistake I made last time was not taking those midday breaks sooner. My son would ask to do one more ride, and rather than following my gut and telling him that we needed to leave for a while to have a swim and some down time, I would let him get in line for Star Tours or something. By the time we took a break, he was fried and so was I - and the last place I want to feel all grumpy and snippy with my kids is at Disneyland. This time, I am going to maximize those morning hours, schedule a sit down character brunch or lunch, leave the park for a few hours to recharge, and then come back for the afternoon/evening.
Have you thought about Mickey's Halloween Party? It'll be happening while you're there.
Oh, and if you're not already aware of the Baby Care centers, they're great. If your 2.5 year old is potty trained, you might not need them so much, but if still in training, they're worth knowing about!