If price isn't an issue check out phil and ted, bob, and maclaren strollers online.
After much research we narrowed it down to two: a kolcraft with adjustable seats (kids can sit facing each other, facing away from each other, three other ways too), and the joovy ultralight caboose.
We got the joovy because our daughter would have outgrown a regular stroller seat too soon after getting it. The joovy is rated higher than the sit n stand and seems more comfortable. You can easily find them for cheaper on craigslist or ebay too. You can try out many styles at babies r us to see how easy they are to steer and maneuver.
The only problem we have is that our three year old can get out of the back jump seat and she's a runner! If your oldest isn't then he will do fine in this style, and they are sitting back to back. Our single stroller was a jeep and we loved that but had problems with the tires deflating often. Good luck!