We went to WDW last year with our 2 year old and almost 5 year old. We decided after much debate to take our 2 umbrellas (one volo one triumph). We were glad we did mainly for taking transportation and for shopping. It was also nice if we split up in that one could take one stroller the other take the other.
With that said, we do DL several times/year and there we walk to and from the parks and we take our double jogging stroller. We much prefer the convenience of 1 stroller, the larger baskets, cup holders, etc except that I will NOT take that thing into the stores. For shopping, the 2 umbrellas win hands down! And, I would not even attempt transportation with it. If your jeep umbrella stroller doesn't offer any extra conveniences over 2 single umbrellas I'd take the 2!
My son is tall and has trouble sleeping in the volo. If I were to do it all over again, I'd get a 2nd triumph or maybe even a step up from there! The mesh seat also doesn't seem to give a lot of support and there is a lot of flexing of the stroller going on (he was 55 lbs on our trip and 47").
Alison