Just returned from WDW. What I recall about
stroller rentals:
The daily cost for a double stroller was $17 - $1 (Disney) on return
Multi-day cost is less 10% - you receive coupons for the # of days purchased. You use a coupon each day at stroller pick-up. The coupon is date stamped on use, so a coupon can be used at any park, any day. In fact, it appears they could even be used at another visit in the future.
The strollers have canopies, they differ slightly from park to park. If I recall AK's were the flimsiest- difficult carrying items on top cover. I believe thay all have pockets and bottle holders on rear. They also have a sleeve for a name placard which you're given at pick-up.
Throughout the parks there are designated stroller parking areas. Be aware, if you leave a stroller elsewhere, it could be taken to a nearby parking area while you're at an event/ride/attraction. It may also be moved to another location within a given parking area. So if you return to your stroller and it's missing look around- it's usually somewhere nearby! Also remember where the parking area is in relation to your entry. many attractions exit a distance from entry, and it's easy to get disoriented in the departing crowds.
My opinion is a stroller is necessary for younger children. Our first day at MK, without a stroller,with a 4 and 5 year old, fatigue set in after about four hours- with a stroller later in the week, they went opening to closing without any let-down. Also not having to carry a back pack made life a lot easier on the adults! This was in Jan., I can only imagine what it's like in warmer times!