We took DD to DL at 17 months and then to WDW at 18 months. Both trips were great and not really difficult at all. My advise would be to make sure your DS will be comfortable enough in his stroller to take a nap when he's tired, if he's the type that will do that, some kids won't. Our trips with DD at those ages were in August and September, pretty hot at both DL and WDW, and a little baby-safe clip on stroller fan was invaluable. If he won't nap in the stroller, but he does regularly nap at home, I'd make absolutely sure you got him back to the room for a nap during the day. Also make sure you pack plenty of his regular snackies, you're not likely to find Gerber Puffs (or whatever toddlers eat these days, my 'baby' is now 7, I don't remember!) easily at WDW, or if you do, you can be sure they will cost double what they would cost at home! My DD was horribly afraid of the characters at that age, liked to view them from a distance but was terrified if they got close, but other than that, she enjoyed it all tremendously and we have wonderful memories of those trips. Have fun!!