My first two are 22 months apart in age so my experience was a little different but I agree with heatherppmom3. Once the newest addition arrives, routine will be everything when it comes to finding time for anything - especially those much needed down times.
I have a 5year old 16 month old who doesn't sleep through the night and due any day! You'll figure out a good routine for you all and will be just fine it may even be easier with them so close!