17 months is pretty young for a big bed, but I know it's hard with the new baby coming. When we moved K (and plan the same with R), we got a readybed (it's a low, inflatable bed/blanket combo) and put it next to her crib. She was so excited to be allowed to nap in her "princess bed" sometimes, and we worked up to regular naps then nights, and finally made it a big deal to move her into her new room with a big bed (with side-rail). We moved her on her 2nd bday, about 3 months before R was born, and really played up the "you get a new room because you're bigger" so she never seemed to notice the baby going into her old room. We had R in the bassinet attachment of the playpen for about 2 months, so that's something to consider if you're trying to buy a little more time before moving your older one out....