We like our Pliko P3, but my kids are 4 years old and 20 months. Your 23 month old might not be comfortable standing on it for very long as the canopy would be in her face (but it is removable). Also, when the infant seat is in the stroller the back must be reclined, which I think inhibits the older child from standing on the rear footboard. My neighbor just got one for her newborn and 22 month old, I'll see how she likes it... We've only had ours for a few months, but we like it because it folds up like an umbrella, is lightweight for traveling, and allows my son to walk or ride if he wants to without me pushing around a half empty double stroller. I hope this helps. You should try to check out out at a local baby store if possible.
My neighbor has taken the cover off of the Pliko and attaches her Graco carseat for the infant who uses the carseat's cover. There actually is room for her 22 month old to ride on the back while the carseat is in place, but it's for short rides only as the toddler usually won't last too long on it. Good luck.