we took our graco double last time as youngest was only 5 months and on a heavy heart monitor, and her brother was only 2.5. (2 in diapers) It was so heavy but I have to say we could not have gone without it. And although some will disagree, people at Disney are just usually so happy to help, be polite and wait as you load, unload each time. By day #2 of our trip we had it down to a science. And being as you are alone, it will afford abit more control of the kiddos too.
I have also owned the Baby Trend and the Joovy sit and stands. I find them to still be very heavy as well as exceptionally long. The Baby Trend is nicer for the toddler as the Joovy seat seems to slide back and forth with no way to secure it. I ended up returning the Joovy and sellign the Baby Trend. <sigh>
This trips the little ones will be 2 and 4. No way my 4 year old would walk (others of mine have with no trouble) so it is an individual child decision.
We are "graduating" to 2 Maclarens this trip. At least they are lightweight when I am left alone with them

and DS4 can actually push his own if he doesn't want to ride! They steer like a dream!
If you rent, still bring a cheap umbrella for to/from parks as you can leave it at rental place until you drop off rental at end of day!
don't know if that was any new information or not, hope it helped.
I'd love to go along and help you if you're looking for a nanny!
