You know your kids best. My oldest DD is an endurance child - biked 7 miles a month before turning 5! She did great at WDW at 4 without a stroller except for day 8 at the parks. She's just so happy to be there, she'll just keep on walking to the next ride or show. We always took a break in the middle of the day. Now my DS who is 3 is another story. We could probably take him to WDW when he's 10 and he'd still want to ride in the stroller! Each kid is unique. If you think they can go wihtout a stroller - and you set up that as your expectation and let them know you believe they can do it - they probably can. But if you think you need the stroller, then bring/rent it.