Last year we rented a double stroller, DS was 5 and DD was 3. This time DS is 6 and DD is 4, so I'm wondering if we'll need one for DD. She just turned 4 in August, so that's a lot of walking - originally I thought we might not need one but now I'm reconsidering. Any thoughts? Do they still sell those red umbrella strollers in the park? I think they were $40 or something like that.