We've travelled with little ones (both ours took their first trip at around 12/13 months) and my first tip would be the most obvious and one I'm sure you've heard before - plan ahead and then be prepared to be flexible. I like to go armed with as much info as possible to that when we get there we can adapt our plans as and when we need to.
Well our plans basically let us have every second day "off" where we have zero plans but I've made notes of the crowd calendar on Touring Plans so we can change our days around if need be 
With regards to the flight - this might be the hardest part to plan for because you have little/no control about timings, etc. Take lots of toys, snacks, drinks and treats! How does your DS like to go to sleep? Ours would always take naps tucked up against our shoulders but turbulence and having to keep seatbelts on made this tricky at times - and would be extremely difficult if you needed to rock/pace to get DS to sleep. On the whole though we found that even though they didn't always sleep when we expected or hoped they would, they did just drift off when they needed to. We've carried some grumpy girls through customs and then waiting to collect bags, etc followed by the trek through MCO so be ready for that - they usually caught up again in the car/bus on the way to our hotel
Thankfully DS is similar to your kids in the sense that he will just curl up and sleep once he doesn't let himself get over tired. He loves to sleep ON me or DH, or on his Nan who is also coming with us. Are there any toys or treats you would recommend to have?
TIme difference - the first day/night is a long one - by the time you're checked in in the afternoon DS ought to be in bed and then the next morning our DDs were awake at 3 or 4am and ready to go! The only way we found to tackle this was to check in and then go out again (not really riding rides but because we've stayed close to MK we've usually ridden the train around MK, taken a look at the castle and eaten at a CS place). It makes your arrival day really long but we found that the fresh air/sunshine + eating that one meal at 'Florida' time before going to bed at 'Florida' time helped us, even if we were tired. The next morning we usually book an early breakfast ADR and plan on getting the most out of those earlier morning wake ups for at least a couple of days. I think the first year we took our eldest DD we all had cereal in the room at about 4.30, took another nap and went off to MK at 8!
It didn't seem to take any of us long to adjust on the way out - and regular breaks/naps and some early nights helped. We did find that when we came home the girls coped better than we did - we would still be wide awake at bedtime and then slow to get up in the mornings!
I think this is what I'm most nervous about. Our flight gets into MCO at 5.05pm local time which would be 10.05pm to DS and he'd usually have 3 hours sleep over him! I suppose best to let him nap on the flight and wake him when we arrive if we could possibly get him to do this!! We'll have to go out for dinner anyway so hopefully he'll manage to stay up with us and then just crash for the night! Fingers crossed!!
The parks - depending on how DS likes to get to sleep, and where you are staying will make a big difference to this. Ours would sleep in the stroller but I tried to make sure they had plenty of 'proper' naps in their beds in the early afternoon too. The only thing to remember here is that it can take a long time to travel across Disney property and there's nothing like a bus ride to send a child to sleep before you even reach your room! For us we had to avoid this because a 10 minute cat-nap on the bus had consequences later on so we choose either to leave early enough that we can get back to the resort before nap time, or we purposefully choose boat rides/walking routes etc to offer pushchair naps. We've strolled around Ft W campground, ridden the boat backwards and forwards between FT W and MK a couple of times, walked from Epcot around the Boardwalk resorts, etc.
We're staying offsite in a pool home with my parents and sister. DH will be driving and he has said he doesn't mind making the journey from park to home for naps and then back to the parks in the evening if we want. Thanks for the advice though, its very very useful!!
A lengthy reply I know but hope something here helps!
And if you've any other questions I'd be happy to try to help
and then we'd head back into the parks for dinner and fireworks etc. This way we'd generally be in the parks till 11pm and back at the hotel in bed by just after midnight. It worked for us.
The thing is, even if you do have experience, you only have it with your own child, not with anyone else's
(we did many of those time-outs with the ladybugs the first year) or whatever it may be, when the going gets tough, change the scene. That hour or two or even three that you surrender for the sake of peace almost always buys you at least double that later in the day 
