I probably wouldnt buy a double, since your oldest is 5 you really wouldnt use it that much. IF I were going to buy something like a double, with kids that age, I would consider the sit n stand since the back seat isnt really a 'stroller' seat. Another thing to consider is the weight of your 5 year old. It may be very heavy to push kids that age in some double strollers.
We are going in April and I am taking two single mac volos I bought- I plan on getting those stroller connectors to make it 'seem' like a double.
I dont like the double we have at home, but I didnt want to buy a new one since we wouldnt use it much after the trip with ds being 4. But by buying two singles and the stroller connectors, I know that we will be able to use one single volo for my dd for the next few years, and we will have the other volo to use for any big trips like wdw for ds. When we are done with them, I will sell them.
I personally do like to have our own strollers down there. The walks from the parks to the buses can be long on tired little legs, and carrying kids and bags just doesnt sound fun to me.
Staci