I'm still debating what to bring on our August trip to WDW. DS will be turning 7 and DD will be 3.5. She REALLY needs to ride and I think DS will want to sometimes as well, so dh wants to haul the P&T. The issue is that we are also going on a cruise at the end of our trip and the P&T is overkill for that. My other options are a Mountain Buggy Urban Double (would be great for the parks, but can't take it on the ship), a Mac Volo, or I could buy something else. I know a lot of people bring 2 single strollers, but I really think DS will be walking most of the time and we won't want to have a stroller with him when we split up.
Have you thought about bringing your Volvo and renting a stroller for your DS? This is what I did last year. - then you aren't lugging your big strollers on the ship - but will have a stroller if you need one for DD.