I want to put a zip line in my backyard for my kids. I'm looking for advice on what type to use, safety tips, and installation advice.
This is in the category with swimming pools, and trampolines, and jungle gyms. There is no way to be completely safe and still have it fun.
Most ziplines have raised ends, with one end lower. The uphill on the downhill end slows down the person. A lighter person tends to travel more slowly, and may stop short of landing point. This can be adjusted by shortening the cable, moving the low point closer to the landing point.
Conversesly a heavy person may come down too fast and slam into the stop at the end. Put more slack in the cable. You can also form a bumper by slitting a hollow core pool noodle, wrapping the bottom end of the cable with it, and then wrapping the noodle with fiber reenforced tape. This gives a 6 foot bumper. Again, test thoroughly. An old matress for 3 on the post at the bottom is also a good idea.
Perodically schedule an inspection: Check the slider axles for wear, the cable for wear, the cable splices at the ends, the attachments to the supports at the ends, the landing area.
Watch it in use, seeing of there are 'almost' accidents.
Liability: Probably a can of worms. If your kids want friends over to play, I would require that their parents take a ride on it.