I took a few hours off of work to check this trail out and it was quite a rewarding experience. Taking the Metro North from Grand Central to Ossining is pretty simple and took ~45 minutes.
The trail itself isn't too exciting and you are walking through people's backyards most of the time, but I found it to be an interesting look into how people live in this part of the state (in addition to the historical significance).
Instead of turning left Quaker Bridge Rd, I continued on the trail for an additional mile. After 10-15 minutes, you should start hearing the rumblings of the New Croton Dam. I'm not sure why this wasn't included in the original trail but this was easily the highlight of the trek for me. It is possible that it was closed due to terrorism concerns when Daniel did it initially. The dam itself is quite an impressive structure and most of my pics were taken there (you can see them here: https://goo.gl/photos/JKCC5abbwNjjS5B87
There is also a park below it that offers a pretty good viewpoint.
After crossing the dam, I made the mistake of continuing down Croton Dam Rd and heading back on Rt 129. This is a BAD idea as there are no sidewalks on this road. If I had cell service I would have called a cab or Uber as it is only a 10 minute drive to Croton Harmon station from this point.
Instead, I'd suggest taking the Aqueduct trail back to the previously mentioned intersection (Quaker Bridge Rd) and continue from there.
Hope this helps!