Our kids were 9, 4, and almost 2 on our trip and we used two strollers. It worked out very well for us and we had no problems. We bought stroller clips in BabiesRUs so we could clip the two strollers together if we needed to split up. (We had two Volos, so they clipped together easily). I found it very difficult to push clipped together (DH didn't think it was that bad), but the only times we split up were when the two little ones were too short for a certain ride. (Our 4 year old was 40", so usually one of us just took the baby and parked the second stroller.)
Sarahbug- Even with a much older child we were all able to stay together in the parks. (We used fastpass and rider switch for any rides the little ones couldn't do, so they only waited a few minutes for us to do them. Occasionally one of us would take them on a nearby attraction with a short line.) If we wanted to give her extra time we all went back to the resort so DH didn't have to deal with two strollers on the bus. One night she and I went out for a mother-daughter night in the MK (a highlight of the trip) and another afternoon I took the two older kids to Epcot. Both times DH stayed with the younger one(s), went swimming, ate, and slept.