Has your child been before? And if so, how did your child react to the crowds?
Though my youngest could have handled it physically, he was overwhelmed and needed a place to hang out. I'm so glad we had the stroller when he was 5. Our next trip isn't Disney (except for Disney Springs), and we are still taking the stroller - for Universal/
Legoland. He'll be three months from 7. BUT - he may need it for emotional reasons so we would rather have one and not need it. 5 seems to be the age when about half of the people will say you need one and half will say you don't. Physically - it depends on the weather, how long the days are, how many days you have, etc. One of my kids didn't use the stroller at all the first day when he was 3. But by the 7th day, he was in the stroller most of the time. Emotionally - it depends on quite a bit too. My youngest has some sensory issues and the stroller was essential. My middle child does not but was worried about getting separated from us, so it was nice for her to have the stroller for that.
Also - think about pacing. You can only go as fast as the slowest person. On the trip when my amazing endurance middle child was 5, the plan was for her to walk the entire time and we knew she could handle it. However, the 2 year old refused to use the stroller (and refused to walk so he was in the sling). This meant we found ourselves pushing around and empty stroller. Once we realized this, we told her to hop in when we had longer walks between things. This sped up our touring significantly. We didn't HAVE to do this, but it helped.
Then there's always the unexpected. One of my kids scraped his foot on the bottom of the wave pool taking out a chunk of skin. It was on day 3 of a 14 day trip. Thankfully, it was the youngest child and he still fit in the stroller.