When we first went our DS were 2 and 4 and we took our double stroller. It was a life saver. Our DS 2 crashed one afternoon for 4 hours in the stroller. It does have a reclining seat - so he was pretty comfy. Even though they are 4 and 6 now - we still take our double stroller. They get tired when we want to "walk with purpose" to our next land/destination. When we are in Fantasyland we park the stroller and walk to the rides since it has a nice heavy concentration of rides to go on.
On our first trip DS 2 was a little nervous about some of the rides, but he was riding with a parent so we just held on and explained some things. Dumbo was a definite favorite. We rode it a number of times. Bugs land was their absolute favorite spot in both parks, they could ride Heimlich over and over.
We took snacks and water into the park with us - goldfish, granola bars, dried fruit, beef jerky and some peanut butter crackers. This helped them to keep their energy up and it made it easier if they didn't like what was offered for lunch at Counter service places. It also gave us some variety since the choices at CS can be very limited.
We did NOT try Matterhorn that first trip - I don't think either the 2 or 4 yr old could handle it. It was down for an extensive refurb anyway. They didn't want to ride it the next time, either. But finally rode it in Dec. and liked it. They roar as loudly as Harold (abominable snowman) does and say hi in monster just like he does.
Child swap and Fast Pass were great for us - you can get a FP for every ticket even if your child can't ride the ride. You go to the FP entrance and ask the CM for a child swap pass and then you or your hubby ride the ride and then you swap - through the fast pass line with your child swap pass and you each have had a chance to ride. BUT you still have 3 FP's left - so you have 3 more chances to ride that particular ride. You could also use 2 tickets for one FP and the other 2 tickets for another/different FP and really maximize your FP's. That way with each FP and child swap you get 2 separate chances to ride! It works - I promise!