M.,
My little guy is 2 and he will have a baby brother by the end of September. I decided on the Sit n Stand stroller, made by Baby Trend. The attachment for an infant seat will fit any of the major brands of infant seat, and the bench in the back will accommodate your almost 2 year old. The bench in the back does have a strap so you can strap her in if you want, or let her choose to sit or stand in the stroller. If you want her to have an actual seat (like one that she can nap in), then this would not be the stroller for you, but if she's big on choices, it's a great idea. I found mine on Craigslist for $20, which is an absolute steal. It's an older model, though, so that's why it was so cheap. You can find newer ones for good prices. I would also suggest looking at Craigslist for the Graco Quattro if that's what you decide upon, because you can find strollers in great shape for much less than they are new.
Good luck!
Amy K