Alex,
We did the trip with an 18 month old, and will shortly do so again with a now 27 month old.
I wish I could tell you there are ways to make it easy, but there probably isn't - although you can make it easier by not worrying about it too much. Suggestions such as small toys, sticker books etc can all help to pass the time - don't bring them all out at once - one every half hour or so should help maintain interest.
We took the car seat and fixed it in the plane. This helped DS to sleep for a couple of hours, but there is an awful lot of activity going on and our two year old will certainly fight sleep for as long as possible.
Definitely bring plenty of snacks and drinks. If you're considering 'drugging' we were advised to use Piriton syrup, but it didn't seem to do much. Tixylix coughs and cold formula seems more effective at instigating drowsiness.
Overall, just take it as it comes - don't get too stressed about others around you - chances are you'll never see them again anyway. Be prepared to walk up and down the aisles an awful lot - the cabin crew are used to this, particularly on Orlando flights.
Also, ensure you make the same preparations for the return flight. It is dangerous to assume that your two year old will sleep most of the return flight because it is overnight. There are just too many interesting distractions.
Have a great time!!
Andy