My best piece of advice is to just take it slowly - enjoy it and take in all in. If your DS wants to go on IASW ten times in a row, just do it. We found this to be our guiding principle when doing Disney with our young children, and it made it so enjoyable. No running around from ADR to ADR - we searched out great counter service options for lunches so we could go at our own time. We did do a couple of character meals, which were great, but we didn't overdo it. We definitely utilized fast passes - long lines and our toddlers never mixed very well.
With regards to napping: You may find that your non-napper needs a little rest at Disney. It's so overwhelming - lots of stimulation. Something that worked great for us was this: When we noticed our DD (then 17 months) needed a nap, my DH pushed her stroller right onto the TTC monorail. It only made two stops, had lots of white noise, and the motion knocked her right out. He'd make some work (or play) calls, or play on his blackberry, while the rest of us enjoyed the park child free for a bit. After a little shut-eye (sometimes on both their parts!) they just got off and met back up with us. Obviously this only works in the MK - but we spent a lot of time there that year.
As far as a stroller is concerned - you'll get a variety of advice on that one. What works for one doesn't work for another. What worked for us was to bring our own umbrella stroller (Maclaren Volo) from home. It was easy to fold and bring on the buses (and in our case the plane.) It was much smaller than the Disney strollers and hence easier to maneuver through the parks and tight spaces - like when you're waiting for a parade or fireworks. It was also easier to locate if we had it parked in a stroller parking area. And at the end of a long day - it's nice to roll your child right up to the bus (or to your car) rather than having to carry them if they're exhausted. And of course it saves you some time in the morning because you don't have to go and get your stroller when you enter the parks.
We have "done Disney" with toddlers more than once - feel free to PM me if you have any other questions. I'd be happy to share not only what worked for us, but what we know works for others and why. You're going to have an amazing trip - I wish I could do those first trips all over again!
Oh! One more little tidbit: The best thing to stash in your park bag for the day: a Ringpop or two.

When things got a little dicey - waiting for a parade or fireworks or on the busride back to the hotel - we unwrapped one of those babies and enjoyed pure silence! I like Ringpops as opposed to regular lollipops because they are bigger (and hence last MUCH longer) and they have a plastic ring, rather than the sticks that our children tended to bite through.

They are a bit messy - so bring those WetWipes! - but I'll take a quiet, happy messy child over an overstimulated antsy loud one any day.

Oh, and I would only bring the red ones - the blue and green ones are messy to the 10th degree!
