I'm an avid babywearer and am planning our third WDW trip since kids. I feel that it's totally doable to go without a stroller, especially if LO will walk some of the time. On our first trip, older DS was 27 mo. Only 3 days. We bought an umbrella stroller in Orlando as we didn't own one. DH pushed it into the park each day, where we parked it and never touched it again. We've never gone during high crowd times, so he was ok to walk about half the time, and I wrapped him whenever he got tired. I wouldn't have bothered with it if we took that trip again.
On our second trip, boys were 9 mo and 4. We dragged the same umbrella stroller back down. Forgot it in the room on our first day, at Epcot, and I had only brought one carrier to the park (mistake!). We stayed through Illuminations, both kids fell asleep, and DH carried the baby in arms back to the bus stop so that I could wrap the 45 lb 4 y/o. From then on (5 day trip) we brought the stroller and a carrier so we would have options. It still spent quite a bit of time in stroller parking, but DS4 would ride in and out of the parks and from one Land to the next some of the time. Baby rode occasionally, but was mostly worn. They will let you wear on some of the slow rides, which is nice, but it was pretty variable.
We're going again in Jan. Kids will be 21 mo and 5. I'm up in the air about whether to bother with one - we may just rent if big boy gets tired one day, and I'll definitely toss a second wrap into my bag.
What works for me may not work for you. DH wears too as long as I wrap the kids on him, so getting tired isn't really an issue. We lived in FL for years, so wrapping in the heat doesn't bother us. We haven't gone to WDW yet in the summer. We also don't usually commando the parks (except the day we forgot the stroller!). We go from RD until mid-afternoon, then relax and have a nice dinner. My older boy has always been a big walker, since we never had a stroller at places like the zoo either. Little guy hasn't been walking long, so we'll see how he does. If any of these things don't apply to you, you might want a stroller. Even if they don't you might want one anyways.
Oh, I've flown dozens of times with kids in carriers. Mine have no metal so I wear right through security - you may have to remove the Ergo to walk through a metal detector. I wear all through the airport and onto the plane. They're supposed to ask you to remove the child for takeoff and landing, but it varies flight to flight. Then I pop them back in to walk back off and get my bags.
Sorry for the novel, but babywearing is one of my areas of expertise!
