I wouldn't get a regular double stroller if I were you. Your older kiddo will only use it for maybe another year - if you're lucky. My kids wanted nothing to do with sitting in a stroller by the time they were 2.5 years old. No sense spending money on something that will be outgrown in a year.
I have the Double Elite Sit 'n Stand stroller from One Step Ahead (onestepahead.com) and LOVE it. We've had it for about 2 years now, use it often, it's in great condition and I have ZERO issues with it. It's a very unique stroller because it's a both a normal double stroller and a Sit 'n Stand style. In the normal mode, the backseat has a 5 point seatbelt, reclines, has a footrest and sunshade. In under 2 minutes, you can convert the backseat area to a traditional Sit 'n Stand style -- with a bench for sitting down facing backward and a platform for standing. This style is great for kids once they turn 3... but you can store the seat parts in the basket so if they decide they want to recline and nap in the middle of the day at the zoo you can turn it into a normal seat in less than a minute. This stroller is the best of both worlds!
An infant 'bucket' seat snaps into the front seat. The front seat reclines, has a tray with cupholder, foot rest and sunshade. There's a parent tray with 2 cupholders. The storage basket is big and easy to get stuff in/out through the sides when a kiddo is sitting in the regular backseat and easy to get to in the Sit 'n Stand mode. It folds easily and is about the same size as my single Graco when folded. It manuvers very well, even with 90 lbs of kid on it (before baby #3 was born my then-2-year-old and then-5-year-old used it). Oh, and my then-2-year-old had no trouble climbing into the backseat once baby sister was born and we put the bucket seat in the front.
We'll continue to use it for at least another year so we definately got our money's worth. It was about the same price as a normal double stroller when I was comparing so it was a no brainer - you definately alot more for the money.