You didn't say how old your kiddos were. We went in August - the boys were 4. I was by myself sometimes when my DH and 11yo cousin were riding some of the rides (or DH may have been by himself). Also occassionally one of the boys would want to ride a ride (like Test Track) and the other wouldn't have any part of it.
We took two Volos. It was great!
If I was by myself, I could park one or both strollers and just walk with the boys. We all tried to stay together, so it was never for more than 30-45 minutes. Usually, we would just stick around the area and check out the gift shop or any of the many other things to do. (Ex/ DH and cousin went on Everest ride - The boys and I did one of the kid passport activities, then went to get the free water they were passing out the coupons for, then went back to the strollers and had a snack, then DH and cousin were done - everyone happy).
There was one time where DH and cousin went to the park earlier than me and the boys. It was no problem to lug the two umbrella strollers - we were very efficient at opening/closing them. Once getting off the bus, the boys took turns pushing each other in the park while I carried the other until we all met up (otherwise I would have just parked one).
We also had a side-by-side umbrella, that pushed liked a dream, but it was really too heavy to take. We took the two single strollers and then recently the family across our street with twin girls, near the same age as our boys, took the strollers. They were very happy in comparing to the other families in their group of 29 (yes 29 - ugh!) and their assortment of strollers.
All that said, I'm not sure I would do the same with an infant and a toddler, but would again with one at least late 2 years or older.
(BTW - my husband thought I had lost my mind by even suggesting pulling out the strollers; now he knows I'm brilliant!)
