If you just want to do the foot section of the Three Sisters Praxis then come to the Volcanoes Day Use Area anytime between 9am and 10:30am. I will have maps with pre-plotted points.
This is a great alternative if you don't have a mountain bike or want to bring the kids. The trails around the volcanoes are well developed and I've captured most of them on the map so you can even get by without a compass.
Just be sure to bring a hat and plenty of sunscreen.