My boys are also 2 years apart and we've done various stroller combos in the parks. I've done:
-sit and stand stroller when they were 21 months and 3 1/2 (not the best option as when the little one reclines the older one can't sit in back, also the older one faces backwards and he wanted to see out the front)
-a very old and very ugly side by side Graco stroller I got for $10 at a yard sale when they were just turned 2 and one month shy of 4 (worked really well! Hideous colors that made it super easy to spot in stroller parking, big basket, seperate recline on seats, folds flat but WIDE so OK but not great in the parks. We were at the WL and were able to roll it right on to the boat and on to the monorail without a problem. On the monorail it just had to be a handicap car but we never had to wait for a 2nd monorail b/c we couldn't get on. This worked well and they were comfy but it was a tiny bit cumbersome on the busses - worth it though as they were comfortable and not fussy).
-the garage sale Graco literally fell apart after that trip so I had to replace it before I went back for a Mom and kids trip with a girlfriend and her kids so I bought a
Chicco Citta Twin side by side umbrella stroller to take with me. The boys were 2 1/2 and 4 at that point. This worked really well for all of our needs. It's not exactly LIGHTWEIGHT at nearly 30 lbs but I had no choice but to have a double since it was just me and my friend and she was bringing her 2 and 4 year olds too. My kids will both GO GO GO at the parks but as soon as you tell them that was our last ride, they want to lay back and go to sleep so renting was out, I needed to be able to push them outside the parks. THis had seperate reclines and seperate canopies (the Graco had one big one). It folded up relatively compact, umbrella style so it was less cumbersome on the busses which was an issue since I was alone. The only negative was that my kids are tall (DH is 6'4" and I'm 5'10") so their combined weight + the weight of the stroller was over 100 lbs so my legs were killing me by the end of the trip!
-Next we took 2 singles for our Christmas week trip figuring it would be easier to navigate crowds without the big wide double (plus the kids were heavier still by then!). The boys were then almost 3 and 4 1/2. We took a Peg Perego Pliko and I bought a new Maclaren Volo. DH and I each pushed one. We came to the conclusion that the Volo was the PERFECT Disney stroller since it was only 8 lbs, folds very tiny, has a carry strap for when it is folded and has a decent basket too. It doesn't recline but our oldest rode in it so no big deal He did fall asleep in it at night and it cradled him really well and he was comfy in it. We would actually race out of attractions to get to the stroller parking to get to push the Maclaren b/c it was so easy to push! Taking 2 singles worked well for us.
-By the next trip the boys were almost 4 and 5 1/2. They were now WAY too heavy for the double so it was 2 singles as our only choice. About 2 weeks before the tip I went to buy another Volo so we'd have 2 to take with us. All I could find was a bright pink one. I was fine with that considering that we don't stroll them anywhere but Disney so who cares...it's convenient and we'd be selling it before long anyway! DH however was adamantly against seeing either of his sons ride in a hot pink stroller.
My youngest was getting too tall for the Pliko, his legs were too long, so I bought a
Chicco C5. We love this stroller too and no more fighting for the Volo b/c DH has claimed this as HIS stroller b/c it's got nice and tall handles. 2 singles worked well again.
-Next trip they were just past 4 and turning 6. It was my Mom and I and she would be riding an ECV so I had to push alone. That meant renting as I couldn't ask my almost 6 year old to walk all day in the heat...he
could do it but he'd be miserable and whiny and that isn't fun for anyone so we rented doubles. Worked great at MGM but at the other parks they fit but it was a tighter fit than made them happy. It was 95+ degrees every day so HOT and sticky being smooshed up together so we heard lots of "he's in my space!" and "he's touching me again!" Probably would have been fine if it wasn't so hot. Again, my kids are big. My 6 year old is 48" and 58 lbs, by 4 year old is about 44" and 48 lbs.
As far as double or single...here's my take having done both. Know your park style as that is what will be the big factor for you. Are you likely to split up and take the kids on different things? If so is it like one of you will do Fantasy Land with the little one while the other takes the older one on Splash Mountain or is it things like the older one will ride Splash while one takes the little one to see the Country Bears or to the playground at Splash? Are the adults likely to split up? By this I mean that DH and I do this...when we arrive at the MK in the am he used to take the kids to Dumbo and I'd head to get a Fast Pass for Buzz and meet them at Dumbo. They'd be at the front of the line so I'd wait outside and take pictures while they ride. Having a double was better for that. When we took 2 singles, we just had the older one walk that little bit and I pushed an empty stroller. If you are likely to split up that way, a double works great. Another double pro is that when you are all together if one of the kids WANTS to walk, you have an adult free to hold a little hand if it is crowded. On the other hand, if you'll be splitting up and each taking the kids to different things then 2 singles is ideal. Two singles are easier in a big crowd so if you are going at a crowded time, consider that. I never had any issues fitting anywhere with a double, the only time I had trouble was on my mom and kids trip which was during the Food and Wine Festival. It was SO crowded on night at Epcot and I just couldn't move b/c people would push around me and step over the kids legs to get in front of the stroller so I could not move...I was totally stuck. I was alone that night so I was really in a jam. I finally ended up yelling at someone "I WANT TO MOVE TOO! PLEASE DON'T STEP OVER MY KIDS!" I think that would have been an issue with any stroller though being alone with no one to help "block" for me and there were an proportionately higher # of people who had been drinking at those stalls all evening. I have never seen World Showcase so crowded as it was that night...not even Christmas week. On the bus, IMHO it's 6 of one, half dozen of the other b/c you either have 2 smaller strollers or one bigger one (an umbrella fold double is not BIG but it's bigger than a single). If you plan on going more than once and you are buying whatever you take...go for 2 singles. The kids will be able to use them longer.
Didn't mean to write a novel but I hope that helped!
We used it exclusively in June for DS 4 and DD 6 and it was a lifesaver. In Nov. 04 we used 2 strollers and that worked well also. But the Joovy ROCKS!!
