When we have gone with two young children who both need a stroller, we have rented two strollers rather than a double. Pushing a double around WDW can be difficult.
Consider if you need the stroller outside of the parks, if so, you might want to rent from an offsite company. They will deliver to your resort, you can use for the length of your stay, the stroller is more comfortable and it is cheaper than renting in the parks. We have rented from Apple multiple times and another popular choice is Kingdom Strollers.