Keep in mind that the umbrella stroller that they sell is rated according to the kolcraft website at 35 lb maximum. If your friend has larger or older children, that option may or may not work.
Disney's rental prices are outrageous, so I wouldn't rely on that option either.
I rented before their prices almost doubled. Now, I refuse and always bring my own. I invested in two good maclarens that have made many trips to Florida. Definitely was worth the investment for me.
If bringing a stroller isn't an option, you could also look into renting from an offsite company. They are more reasonably priced and I believe they'll drop off at your hotel.